CA1240187A - Paper forming machines - Google Patents
Paper forming machinesInfo
- Publication number
- CA1240187A CA1240187A CA000458642A CA458642A CA1240187A CA 1240187 A CA1240187 A CA 1240187A CA 000458642 A CA000458642 A CA 000458642A CA 458642 A CA458642 A CA 458642A CA 1240187 A CA1240187 A CA 1240187A
- Authority
- CA
- Canada
- Prior art keywords
- cover
- wire
- lead
- foil cover
- foil
- 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
- D21F9/00—Complete machines for making continuous webs of paper
- D21F9/003—Complete machines for making continuous webs of paper of the twin-wire type
-
- 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
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
- D21F1/00—Wet end of machines for making continuous webs of paper
- D21F1/48—Suction apparatus
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- Paper (AREA)
Abstract
ABSTRACT
"IMPROVEMENTS IN OR RELATING TO PAPER FORMING MACHINES"
In a twin wire paper forming machine an endless top wire (14) passes round a lead-in roll (12) and meets a bottom wire (15) in the region of a lead-in-foil cover (1). The two wires pass over a secondary foil cover (4) which presents alternately solid and open areas to create pulsating pressure on stock between the wires, and then below a secondary trailing cover (10) whose leading edge doctors water on the top wire into an autoslice (9), and the top wire (14) is separated from the bottom wire (15) in the region of a sheet transfer box (11) to pass round a drive roll (13) and return to the lead-in roll. The leading edge of the transverse bars (41) or blades of the secondary foil cover (4) doctor water off the bottom wire. The secondary foil cover (4) and the secondary trailing cover (10) establish successively sharper downwardly forwardly and upwardly forwardly convex paths for the wires which promote dewatering. A primary trailing cover (8) and a primary autoslice (7) can additionally be disposed above the top wire between the lead-in-foil cover (1) and the secondary foil cover (4). The lead-in-foil cover and the secondary foil cover can form parts of a composite adjustably mounted unitary structure.
"IMPROVEMENTS IN OR RELATING TO PAPER FORMING MACHINES"
In a twin wire paper forming machine an endless top wire (14) passes round a lead-in roll (12) and meets a bottom wire (15) in the region of a lead-in-foil cover (1). The two wires pass over a secondary foil cover (4) which presents alternately solid and open areas to create pulsating pressure on stock between the wires, and then below a secondary trailing cover (10) whose leading edge doctors water on the top wire into an autoslice (9), and the top wire (14) is separated from the bottom wire (15) in the region of a sheet transfer box (11) to pass round a drive roll (13) and return to the lead-in roll. The leading edge of the transverse bars (41) or blades of the secondary foil cover (4) doctor water off the bottom wire. The secondary foil cover (4) and the secondary trailing cover (10) establish successively sharper downwardly forwardly and upwardly forwardly convex paths for the wires which promote dewatering. A primary trailing cover (8) and a primary autoslice (7) can additionally be disposed above the top wire between the lead-in-foil cover (1) and the secondary foil cover (4). The lead-in-foil cover and the secondary foil cover can form parts of a composite adjustably mounted unitary structure.
Description
12401~7 DESCRIPTION
"IMPROVE~ENTS IN OR RErArrIl~G TO PAPER FOR~ING MACHIN~"
_ _ The present invention relates to twin wi,e pape.
forming machines and in particular to dewatering apparatus therefor.
In a two-wire paper forming machine a bottom wire passes over a lead-in-foil and moves along a path towards and over a sheet transfer box. In the region of the lead-in-foil an endless top wire after passing round a lead-in roll is brought into contact with -the top wire and is subsequently separated from th~ bottom wire in the re~ion of the transfer box and is passed round a drive roll whence it returns to the lead-in roll. Stock on the bottom wire is contained ~etween the top and bottom wires and water is expelled from the stock d~ring passage of the wires between the lead-in-foil and the sheet transfer box.
In some twin wire paper forming rnachines a contact element has been provided above the path of the wires between the lead-in-foil and the sheet transfer box to promote dewatering. Water expelled has fallen under gravitv>and dewatering has been further prom~ted by i~ providing the contact element or cover with a '' discontinuous wire engaging surface with or without suction to promote dewatering in an up~ard direction.
-~~'However, such discontinllous surface has in practice had the disadvantage that slots or perforations forming the discontinuous sur-face could become plugged or blocked `--~ under certain conditions especially when used in 'conjunction with groundwood stock with a high fines content thereby decreasing the dewatering action and creating oper,-ting pl-ob~eins and rendering the productio;l of high quality, and even uniform quality, paper dificult to at~ain.
~\
~, 12~U18~
--2~
According to the present invention there is provided a twin wire paper forming m~chine in which a bottom wire passes over a lead-in-foil and over a sheet transfer box downstream theref~om, and an endless top wire which turns over a lead-in roll and meets the botto~ wire in the region of the lead-in-foil cover and is separated from the bottom wire in the region of the sheet transfer box to pass over a drive roll and return to the lead-in roll, and the bottom wire passes over a secondary foil cover which is disposed downstream of the lead-in--foil cover and has alternately solid and open bottom wire engaging areas and the top wire passes below a trailing cover which is disposed downstream of the secondary foil cover and has a continuous top wire engaging surface of which the leading edge serves to doctor water on the top wire into a secondary autoslice.
Preferably the leading edge of the sheet transfer box is immediately upstream of the point where the top wire is separated from the stock retained on the bottom wire.
The sheet transfer box preferably has a slo-'ted or perforated cover and a vacuum is created therein sc that suction is applied to the stock before and after the point of separa~ion o~ the top and bo~tom wires which is somewhere midway of the slotted or perforated suction area.
Preferably the lead--in-foil cover has a curved surface and the tension of the wires presses the two `- ~ wires together ~o start a first dewatering action. The ` lead-in-foil can have as wire engaging surface eit:her a blan~;>or continuousJcover or a slotted cover. q`he slotted cover can be used with or without a VaCU-lm created in the box below it. In the former case, when the cover can be, for exa~ple, a cer~ic, only upward ~ewatering results, whilst in tile latter case both upward and downward dewa~ering takes place.
124(~ 37 The 21ternating solid and open areas of the secondary foil cover give rise to pulses which are beneficial to paper formation. These alternating solid and open areas can be created by a series of transverse bars or transverse blades: either arrangement imparts a pulsating pressure to the wires to expel water alternately upwardly and downwardly~ A short contact timc between the bottom wire and each bar or blade gives a pressure pulse to the stock which is beneficial to ~ood paper formation.
The downward -flow doctored from the bottom wire by the leading edges of the foil strips or bars, or blades, forming the secondary foil cover may be encouraged by introducing a vacuum into the secondary lS foil bo~ below the cover. The water pushed upwardly through the top wire is doctored o~f it by the leading edge OL the secondary trailing cover into the secondary autoslice and upwardly into a secondary chamber or saveall, preferably with vacuum assistanceO
The secondary trailing cover is preferahly blan]c, that is to say, it presents a continuous top wire engaging surface, and therefore stoc:k that is pressed between the two wires is now dewatered in a downward direction. The secondary trailing cover is preferably ~5 ceramic, but can equally well be of any material ~~~conventionally used for static wire contacting ele~ents used in a paper machine former. The radius of curvature of the secondary trailing cover is preferably smaller than that of the secondary foil cover in order -to increase the press~re on the stock between the wires. The sheet transfer box preerably has a conveY.
surface and has a vacuum app]ied thereto to assure transfer of the sheet of paper to the bottom wire.
Whilst all the water expelled upwardly can be doctored by the leading edge of the secondary trailing lZ40~87 ~4--cover nd withdrawn by the secondary autoslice, a further or primary trailing cover and a further or primary autoslice can be provided above the top wire intermediate the lead-in-foil and the secondary foil cover. The primary trailing cover is preferably solid or blan)~, that is to say, it presents a continuous top wire engaging surface, and is preferably convex. ~he doctored water removed by the primary trailing cover proceeds into a primary autoslice chamber or saveal], preferably with light vacuum assistance.
The lead-in roll is provided with upward and downward movement~ The lead-in-foil and secondary foil are provided witil an adjusting mechanism which enahles them to be moved up and down and to rotate with respect to the wire line.
P~eferably lneans are provided for increasing or reducing the width of the opening of the or each autoslice. TheJor each~autoslice is preferably inclined with respect to the wire line and preferably at an acute angle with respec-t thereto.
The present invention will be further described by way of example with reference to the accompanying drawings, in which:
Fig.1 is a general sectional elevational view of a tWill wire paper forming machine according to one --~~embodiment of the invention, Fig.2 is a detail of the machine of Fig.1 to a larger scale, `~ Fig.3 is a detail sectional elevation generally `corresponding to Fig.2 of part of a twin wire paper forming machine according to a second embodiment of the invention, and Fig.4 is a detail view of part of ~he secondary trailing cover of both the embodimellts of Figs. 1 and
"IMPROVE~ENTS IN OR RErArrIl~G TO PAPER FOR~ING MACHIN~"
_ _ The present invention relates to twin wi,e pape.
forming machines and in particular to dewatering apparatus therefor.
In a two-wire paper forming machine a bottom wire passes over a lead-in-foil and moves along a path towards and over a sheet transfer box. In the region of the lead-in-foil an endless top wire after passing round a lead-in roll is brought into contact with -the top wire and is subsequently separated from th~ bottom wire in the re~ion of the transfer box and is passed round a drive roll whence it returns to the lead-in roll. Stock on the bottom wire is contained ~etween the top and bottom wires and water is expelled from the stock d~ring passage of the wires between the lead-in-foil and the sheet transfer box.
In some twin wire paper forming rnachines a contact element has been provided above the path of the wires between the lead-in-foil and the sheet transfer box to promote dewatering. Water expelled has fallen under gravitv>and dewatering has been further prom~ted by i~ providing the contact element or cover with a '' discontinuous wire engaging surface with or without suction to promote dewatering in an up~ard direction.
-~~'However, such discontinllous surface has in practice had the disadvantage that slots or perforations forming the discontinuous sur-face could become plugged or blocked `--~ under certain conditions especially when used in 'conjunction with groundwood stock with a high fines content thereby decreasing the dewatering action and creating oper,-ting pl-ob~eins and rendering the productio;l of high quality, and even uniform quality, paper dificult to at~ain.
~\
~, 12~U18~
--2~
According to the present invention there is provided a twin wire paper forming m~chine in which a bottom wire passes over a lead-in-foil and over a sheet transfer box downstream theref~om, and an endless top wire which turns over a lead-in roll and meets the botto~ wire in the region of the lead-in-foil cover and is separated from the bottom wire in the region of the sheet transfer box to pass over a drive roll and return to the lead-in roll, and the bottom wire passes over a secondary foil cover which is disposed downstream of the lead-in--foil cover and has alternately solid and open bottom wire engaging areas and the top wire passes below a trailing cover which is disposed downstream of the secondary foil cover and has a continuous top wire engaging surface of which the leading edge serves to doctor water on the top wire into a secondary autoslice.
Preferably the leading edge of the sheet transfer box is immediately upstream of the point where the top wire is separated from the stock retained on the bottom wire.
The sheet transfer box preferably has a slo-'ted or perforated cover and a vacuum is created therein sc that suction is applied to the stock before and after the point of separa~ion o~ the top and bo~tom wires which is somewhere midway of the slotted or perforated suction area.
Preferably the lead--in-foil cover has a curved surface and the tension of the wires presses the two `- ~ wires together ~o start a first dewatering action. The ` lead-in-foil can have as wire engaging surface eit:her a blan~;>or continuousJcover or a slotted cover. q`he slotted cover can be used with or without a VaCU-lm created in the box below it. In the former case, when the cover can be, for exa~ple, a cer~ic, only upward ~ewatering results, whilst in tile latter case both upward and downward dewa~ering takes place.
124(~ 37 The 21ternating solid and open areas of the secondary foil cover give rise to pulses which are beneficial to paper formation. These alternating solid and open areas can be created by a series of transverse bars or transverse blades: either arrangement imparts a pulsating pressure to the wires to expel water alternately upwardly and downwardly~ A short contact timc between the bottom wire and each bar or blade gives a pressure pulse to the stock which is beneficial to ~ood paper formation.
The downward -flow doctored from the bottom wire by the leading edges of the foil strips or bars, or blades, forming the secondary foil cover may be encouraged by introducing a vacuum into the secondary lS foil bo~ below the cover. The water pushed upwardly through the top wire is doctored o~f it by the leading edge OL the secondary trailing cover into the secondary autoslice and upwardly into a secondary chamber or saveall, preferably with vacuum assistanceO
The secondary trailing cover is preferahly blan]c, that is to say, it presents a continuous top wire engaging surface, and therefore stoc:k that is pressed between the two wires is now dewatered in a downward direction. The secondary trailing cover is preferably ~5 ceramic, but can equally well be of any material ~~~conventionally used for static wire contacting ele~ents used in a paper machine former. The radius of curvature of the secondary trailing cover is preferably smaller than that of the secondary foil cover in order -to increase the press~re on the stock between the wires. The sheet transfer box preerably has a conveY.
surface and has a vacuum app]ied thereto to assure transfer of the sheet of paper to the bottom wire.
Whilst all the water expelled upwardly can be doctored by the leading edge of the secondary trailing lZ40~87 ~4--cover nd withdrawn by the secondary autoslice, a further or primary trailing cover and a further or primary autoslice can be provided above the top wire intermediate the lead-in-foil and the secondary foil cover. The primary trailing cover is preferably solid or blan)~, that is to say, it presents a continuous top wire engaging surface, and is preferably convex. ~he doctored water removed by the primary trailing cover proceeds into a primary autoslice chamber or saveal], preferably with light vacuum assistance.
The lead-in roll is provided with upward and downward movement~ The lead-in-foil and secondary foil are provided witil an adjusting mechanism which enahles them to be moved up and down and to rotate with respect to the wire line.
P~eferably lneans are provided for increasing or reducing the width of the opening of the or each autoslice. TheJor each~autoslice is preferably inclined with respect to the wire line and preferably at an acute angle with respec-t thereto.
The present invention will be further described by way of example with reference to the accompanying drawings, in which:
Fig.1 is a general sectional elevational view of a tWill wire paper forming machine according to one --~~embodiment of the invention, Fig.2 is a detail of the machine of Fig.1 to a larger scale, `~ Fig.3 is a detail sectional elevation generally `corresponding to Fig.2 of part of a twin wire paper forming machine according to a second embodiment of the invention, and Fig.4 is a detail view of part of ~he secondary trailing cover of both the embodimellts of Figs. 1 and
2, and of Fig.3, to a larger scale.
Referring first to Figs. 1 and 2, a twin wire paper forming machine comprises an endless top wire 1~
entrained around rolls, including a lead-in roll 12 and a drive roll 13. The top wire 14 meets a bottom wire 15 over a convex lead-in-foil cover 1 of a lead-in-foil body 2. The wires move in a direction indicated by the arrows ~ The curved surface of the lead-in-foil covc!r 1 and the tension of the wires press the two wires together and start a Eirst dewatering action of stock interposed between the two wires. Where a blanl; cov~r is employed for the lead-in-foil such cover presents a continuous wire engaging surface and only upward dewatering will occur in that region. Where a slotted cover is employed both upward and downward dewaterins will ta~e place there.
A primary trailing cover 3 is positioned inside the top wire downstream of the lead-in-foil and is blank and presents a continuous top wire engaginy surface. A
primar~ autoslice 7 is disposed upstream of the primary -trailing cover 8 and a leading edge of the primarytrailing cover 8 serves to doctor water off the top wire 1~ and into the primary aùtoslice 7. The doctored white water proceeds into the autoslice chamber or -~
saveall 71 assisted by ligh~ vacuum in the chamber.
```` 25 The primary trailing cover~is preferably convex.
-~~ A secondary foil cover 4 is disposed downstream of the primary trailiny cover 8 adjacent the bottom wire 15. The secondary foil cover 4 is convex and comprises ` ~ a series of spaced apart foils ~1 which extend across the width of the wires. The alternating solid and open spaces of the cover generate pulses in the stocl~ as it moves over the cover. This has a beneficial action to paper formation. rhe alternating pulses cause the stock between the wires to be dewatered ~oth upwards and downwards. T;1e downward flow is doctored from the 12~ 87 bottom wire by the leading edges oE the foils 41, and this downward flow can be encouraged by introducing vacuum into the secondary foil. box 5.
A secondary trailing cover 10 is disposed downstream of the secondary foi.l cover ~ and adjacent the top wi~e 14. A secondary autoslice 9 is disposed upstream of the secondary trail;.ng cover 10 and a leading edge 101 (see Fig~4) of ~he secondary trailing cover 10 doctors water pushed up througll the top wire by the secondary foil cover 4 into the secondary autoslice 9. This upward flow yoes into a secondary chamber or saveall 91 and is assisted by a vacuum created in the chamber 91.
After having passed over the convex secondary foil lS cover 4 the two wires are pressed against the secondary traili.ng cover 10 whi.ch is blank, that is to say, it presents a con-~inuous top wire engaging surface, so that the stock is pressed between the two wires and is now dewatered in a downward direction. The radius of curvature of the secondary trailing cover 10, which can be a ceramic or any material conventionally used or static wire contacting elements used in a paper machine former, is smaller than that of the secondary oil cover 4 whereby to incrc2se the pressure on the stoc]~
between tlle wiresO After ~heir contact with the conve~
_-secondary trailing cover 10 the bottom wire comes into contact witn the perforated surface of a sheet transer box 11 wi-thin which a vacuum is created. Due to ~he resultant suction applied through the bottom wire to 30 ~.the paper sheet, transfer of the paper sheet to the bottcm wire is ensured. The top wire separates from ,~ the sheet in the re~ion of~and preferably approximately centrally over~the transfer box 11.
The lead-in roll 12 is provided with upward and downward movement which permits the top wire 14 to lZ401~
cover or ~ cover the lead-in-foil l. Increasing the area covered increases the drainage whilst decreasing the area decreases the drainage. The lead-in-Eoil eover l and the secondary foil cover 4 are provided with adjustable mounting as a~ 3, 6 respectively enablin~ the eovers to be moved up and do~n and rotated with respect to the wire line.
The primary and secondary autoslices 7, 9 are provided with an adjusting mechanism as at 72, 92 respectively for increasing or decreasing the width o~
the autoslice opening.
Referring now to Fig.3, in a twin wire paper forming nachine according to a second embodiment or the invention, the lead-in-foil body 2 and the secondary foil body 5 are combined in a unitary structure 30.
The bottom wire 15 passes ovei the lead-in-foil cover lj which in t:his embodiment is blank or continuous and convex, and there meets the top wire 14 after passing round the lead-in roll 12. Downstream o~ the lead-in-~0 foil cover is the secondary foil cover 4 whichcomprises a plurality of spaced blades 42, preferably abou-~ six as shown, extending transversely across the width of the wires. The blades 42 in combination establish a general]y convex path for the wires and present alternately solid and open bottom wire engaging --~areas. Downstream of the secondary foil cover is a secondary trailing cover lO which is solid, that is to say, it presents a continuous wire engaging surface, "~ ana establishes a further generally convex path for the `-wires. Upstream of the secondary trailing cover is the seeondar~- autoslice 9 leading to the secondary autoslice chamber or saveall 9l. Downstream of the secondary trailing cover lO the wires pass along a path similar to tha-t shown in Fig.l to the sheet transfer box ll which is no1: shown in Fig.3.
:12~ L87 During passage of the wires over th~ lead-in-foil l a first dewatering of stock between t:he wires occurs and water is expelled in an upward dlrection, followed by expulsion in both upward and downward directions.
S The radius of curvature of the path over the secondary foil cover 4 is preferably shorter than that of the lead-in-foil cover l, and, similarly, that of the secondary trailing cover lO is shorter than that of the secondary foil cover 4: the combined action of all these wire contact elements is to press the wires towards one another and thereby press the stock therebetween to expel water therefrom.
~ hilst passing over the secondary foil cover 4, the successive action of the blades 42 and the open spaces therebe'.ween is to subject the wi,-es to a pulsating pressure which e~pels water successively upwardly and downwardly. Water eY.pelled do~nwardly through the bottom wire is doc~ored by the leading transverse edge OL each of the bars 42 and descends under gravity.
Whilst water expelled upwardly through the top wire during passage of t'ne ~ires over the secondary ~oil cover 4 collects above the top wire, it ls doctored by the leading edge lOl (see Fig.4) of the secondary trailing cover lO and flows through the secordary autoslice 9 into the secondary autoslice chamber or saveall 91 ~ith vacuum assistance.
The unitary structure 30 comprising the lead-in-foil body 2 and the secondary foil cover body 4 is pivotally mounted at 31, and adjusting means 32 are 30 ` provided whereby the position and angle of incliration can be set as desired. The secondary autoslice 9 is provided wlth an interchangeable mouthpiece 93 whereby the width, and if necessaxy, the shape of the opening, can be chan~ed as may be desired in order to obtain optimum operating conditions in removal of all the i240187 g doctored water without inclusion of excessive air therewith. Such mouthpiece 93 may conveniently be of a high density plastics polymer such as polyethylene, Similarly, the secondary trailing cover 10 may be interchangeable, and may be of ceramic or of any material conventionally used for static wire contactiny elements used in a paper machine former. Likewise, each of the blades ~2 of the secondary foil cover may be of ceramic or stainless steel, alone or covered or tipped with tungsten carbide.
The leading edge 101 of the secondary trailing cover 10 beneficially doctors off any fibres from and has a cleaning action on the upper surface of the top wire 1~. Moreover, the top wire 14 has a reciprocal cleaning action on the secondary trailing cover 1O.
A twin wire paper forming machine e.nbodying the present invention can have the advantage that upward dewatering is done only by means of at least one autoslice; autoslices are excellent at removing water and highly resistant to plugging. The inclination of the autoslice channel enables the speed of the dewatered stock imparted by the wires to be used to move the water into an autoslice chamber or saveall.
The high water speeds in the channel promote clean]iness, and the speed of the stock carries the water upwards into the chamber or saveall, thus requiring at best only a small amount of vacuum assistance. The upward and downward pressure pulses ~ imparted on the two wires can improve the formation of the paper produced. The adjustment provided permits use of the forming machine for a wide range of paper making applications, and renders it suitable for high and low speed and for producing both heavy and light weight paper. During all the twin wire paper formation process, the wires are in contact with stationary ~Z4~ ~87 elements only such as foils and covers. No rolls are in contact with the wires during the ~rocess of dewatering, and this is especially valuable at high speeds where vibration is avolded, and also at all speeds as problems caused by unclean rolls can be avoided. Haviny static elements only in contact with wires during the process of dewatering is especially beneficial when producing paper which must be ree fro~n pinholes. The dewatering capacity of a twin wire paper forming Dlachine can be high as a result of the use o lead-in-foil cover and a secondary foil cover. The continuo~s increase of curvature of the path of ~he ires contributes to an increase in the dewatering capacity of the twin wire paper forming machine. Sheet transfer can be excellent due to vacuum transfer on the transf2r box and due ~o the initial action of downward dewatering created by the secondary trailing cover.
Referring first to Figs. 1 and 2, a twin wire paper forming machine comprises an endless top wire 1~
entrained around rolls, including a lead-in roll 12 and a drive roll 13. The top wire 14 meets a bottom wire 15 over a convex lead-in-foil cover 1 of a lead-in-foil body 2. The wires move in a direction indicated by the arrows ~ The curved surface of the lead-in-foil covc!r 1 and the tension of the wires press the two wires together and start a Eirst dewatering action of stock interposed between the two wires. Where a blanl; cov~r is employed for the lead-in-foil such cover presents a continuous wire engaging surface and only upward dewatering will occur in that region. Where a slotted cover is employed both upward and downward dewaterins will ta~e place there.
A primary trailing cover 3 is positioned inside the top wire downstream of the lead-in-foil and is blank and presents a continuous top wire engaginy surface. A
primar~ autoslice 7 is disposed upstream of the primary -trailing cover 8 and a leading edge of the primarytrailing cover 8 serves to doctor water off the top wire 1~ and into the primary aùtoslice 7. The doctored white water proceeds into the autoslice chamber or -~
saveall 71 assisted by ligh~ vacuum in the chamber.
```` 25 The primary trailing cover~is preferably convex.
-~~ A secondary foil cover 4 is disposed downstream of the primary trailiny cover 8 adjacent the bottom wire 15. The secondary foil cover 4 is convex and comprises ` ~ a series of spaced apart foils ~1 which extend across the width of the wires. The alternating solid and open spaces of the cover generate pulses in the stocl~ as it moves over the cover. This has a beneficial action to paper formation. rhe alternating pulses cause the stock between the wires to be dewatered ~oth upwards and downwards. T;1e downward flow is doctored from the 12~ 87 bottom wire by the leading edges oE the foils 41, and this downward flow can be encouraged by introducing vacuum into the secondary foil. box 5.
A secondary trailing cover 10 is disposed downstream of the secondary foi.l cover ~ and adjacent the top wi~e 14. A secondary autoslice 9 is disposed upstream of the secondary trail;.ng cover 10 and a leading edge 101 (see Fig~4) of ~he secondary trailing cover 10 doctors water pushed up througll the top wire by the secondary foil cover 4 into the secondary autoslice 9. This upward flow yoes into a secondary chamber or saveall 91 and is assisted by a vacuum created in the chamber 91.
After having passed over the convex secondary foil lS cover 4 the two wires are pressed against the secondary traili.ng cover 10 whi.ch is blank, that is to say, it presents a con-~inuous top wire engaging surface, so that the stock is pressed between the two wires and is now dewatered in a downward direction. The radius of curvature of the secondary trailing cover 10, which can be a ceramic or any material conventionally used or static wire contacting elements used in a paper machine former, is smaller than that of the secondary oil cover 4 whereby to incrc2se the pressure on the stoc]~
between tlle wiresO After ~heir contact with the conve~
_-secondary trailing cover 10 the bottom wire comes into contact witn the perforated surface of a sheet transer box 11 wi-thin which a vacuum is created. Due to ~he resultant suction applied through the bottom wire to 30 ~.the paper sheet, transfer of the paper sheet to the bottcm wire is ensured. The top wire separates from ,~ the sheet in the re~ion of~and preferably approximately centrally over~the transfer box 11.
The lead-in roll 12 is provided with upward and downward movement which permits the top wire 14 to lZ401~
cover or ~ cover the lead-in-foil l. Increasing the area covered increases the drainage whilst decreasing the area decreases the drainage. The lead-in-Eoil eover l and the secondary foil cover 4 are provided with adjustable mounting as a~ 3, 6 respectively enablin~ the eovers to be moved up and do~n and rotated with respect to the wire line.
The primary and secondary autoslices 7, 9 are provided with an adjusting mechanism as at 72, 92 respectively for increasing or decreasing the width o~
the autoslice opening.
Referring now to Fig.3, in a twin wire paper forming nachine according to a second embodiment or the invention, the lead-in-foil body 2 and the secondary foil body 5 are combined in a unitary structure 30.
The bottom wire 15 passes ovei the lead-in-foil cover lj which in t:his embodiment is blank or continuous and convex, and there meets the top wire 14 after passing round the lead-in roll 12. Downstream o~ the lead-in-~0 foil cover is the secondary foil cover 4 whichcomprises a plurality of spaced blades 42, preferably abou-~ six as shown, extending transversely across the width of the wires. The blades 42 in combination establish a general]y convex path for the wires and present alternately solid and open bottom wire engaging --~areas. Downstream of the secondary foil cover is a secondary trailing cover lO which is solid, that is to say, it presents a continuous wire engaging surface, "~ ana establishes a further generally convex path for the `-wires. Upstream of the secondary trailing cover is the seeondar~- autoslice 9 leading to the secondary autoslice chamber or saveall 9l. Downstream of the secondary trailing cover lO the wires pass along a path similar to tha-t shown in Fig.l to the sheet transfer box ll which is no1: shown in Fig.3.
:12~ L87 During passage of the wires over th~ lead-in-foil l a first dewatering of stock between t:he wires occurs and water is expelled in an upward dlrection, followed by expulsion in both upward and downward directions.
S The radius of curvature of the path over the secondary foil cover 4 is preferably shorter than that of the lead-in-foil cover l, and, similarly, that of the secondary trailing cover lO is shorter than that of the secondary foil cover 4: the combined action of all these wire contact elements is to press the wires towards one another and thereby press the stock therebetween to expel water therefrom.
~ hilst passing over the secondary foil cover 4, the successive action of the blades 42 and the open spaces therebe'.ween is to subject the wi,-es to a pulsating pressure which e~pels water successively upwardly and downwardly. Water eY.pelled do~nwardly through the bottom wire is doc~ored by the leading transverse edge OL each of the bars 42 and descends under gravity.
Whilst water expelled upwardly through the top wire during passage of t'ne ~ires over the secondary ~oil cover 4 collects above the top wire, it ls doctored by the leading edge lOl (see Fig.4) of the secondary trailing cover lO and flows through the secordary autoslice 9 into the secondary autoslice chamber or saveall 91 ~ith vacuum assistance.
The unitary structure 30 comprising the lead-in-foil body 2 and the secondary foil cover body 4 is pivotally mounted at 31, and adjusting means 32 are 30 ` provided whereby the position and angle of incliration can be set as desired. The secondary autoslice 9 is provided wlth an interchangeable mouthpiece 93 whereby the width, and if necessaxy, the shape of the opening, can be chan~ed as may be desired in order to obtain optimum operating conditions in removal of all the i240187 g doctored water without inclusion of excessive air therewith. Such mouthpiece 93 may conveniently be of a high density plastics polymer such as polyethylene, Similarly, the secondary trailing cover 10 may be interchangeable, and may be of ceramic or of any material conventionally used for static wire contactiny elements used in a paper machine former. Likewise, each of the blades ~2 of the secondary foil cover may be of ceramic or stainless steel, alone or covered or tipped with tungsten carbide.
The leading edge 101 of the secondary trailing cover 10 beneficially doctors off any fibres from and has a cleaning action on the upper surface of the top wire 1~. Moreover, the top wire 14 has a reciprocal cleaning action on the secondary trailing cover 1O.
A twin wire paper forming machine e.nbodying the present invention can have the advantage that upward dewatering is done only by means of at least one autoslice; autoslices are excellent at removing water and highly resistant to plugging. The inclination of the autoslice channel enables the speed of the dewatered stock imparted by the wires to be used to move the water into an autoslice chamber or saveall.
The high water speeds in the channel promote clean]iness, and the speed of the stock carries the water upwards into the chamber or saveall, thus requiring at best only a small amount of vacuum assistance. The upward and downward pressure pulses ~ imparted on the two wires can improve the formation of the paper produced. The adjustment provided permits use of the forming machine for a wide range of paper making applications, and renders it suitable for high and low speed and for producing both heavy and light weight paper. During all the twin wire paper formation process, the wires are in contact with stationary ~Z4~ ~87 elements only such as foils and covers. No rolls are in contact with the wires during the ~rocess of dewatering, and this is especially valuable at high speeds where vibration is avolded, and also at all speeds as problems caused by unclean rolls can be avoided. Haviny static elements only in contact with wires during the process of dewatering is especially beneficial when producing paper which must be ree fro~n pinholes. The dewatering capacity of a twin wire paper forming Dlachine can be high as a result of the use o lead-in-foil cover and a secondary foil cover. The continuo~s increase of curvature of the path of ~he ires contributes to an increase in the dewatering capacity of the twin wire paper forming machine. Sheet transfer can be excellent due to vacuum transfer on the transf2r box and due ~o the initial action of downward dewatering created by the secondary trailing cover.
Claims (5)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In a twin wire paper forming machine having endless top and bottom forming wires disposed to travel together over a substantially curvilinear forming zone from about where the top wire meets the bottom wire and the wires converge in the region of a lead-in-foil cover within the bottom wire to about where the wires part downstream of a sheet transfer box within the bottom wire, the combination comprising:
the lead-in-foil cover is blank;
a blank stationary secondary trailing cover is disposed within the top wire intermediate the lead-in-foil cover and the sheet transfer box, said secondary trailing cover being curved upwardly forwardly and pressed into the top wire to define a convex path for the wires to travel thereover;
primary and secondary autoslices operatively disposed within the top wire intermediate the lead-in-foil cover and secondary trailing cover;
a primary trailing cover disposed within the top wire immediately following the primary autoslice to engage the inner surface of the top wire;
a secondary, convexly curved foil cover disposed within the bottom wire and pressed thereinto intermediate the primary and secondary autoslices to define, in conjunction with the primary and secondary trailing covers, a downwardly forwardly convex path for the wires to travel thereover.
the lead-in-foil cover is blank;
a blank stationary secondary trailing cover is disposed within the top wire intermediate the lead-in-foil cover and the sheet transfer box, said secondary trailing cover being curved upwardly forwardly and pressed into the top wire to define a convex path for the wires to travel thereover;
primary and secondary autoslices operatively disposed within the top wire intermediate the lead-in-foil cover and secondary trailing cover;
a primary trailing cover disposed within the top wire immediately following the primary autoslice to engage the inner surface of the top wire;
a secondary, convexly curved foil cover disposed within the bottom wire and pressed thereinto intermediate the primary and secondary autoslices to define, in conjunction with the primary and secondary trailing covers, a downwardly forwardly convex path for the wires to travel thereover.
2. A twin wire paper forming machine according to claim 1, in which the radius of curvature of the convex path established by the secondary trailing cover is smaller than that established by the secondary foil cover.
3. In a twin wire paper forming machine in which an end-less bottom wire passes over a lead-in-foil cover, and over a sheet transfer box downstream of the lead-in-foil cover, and an endless top wire turns over a lead-in roll and meets the bottom wire in the region of the lead-in-foil cover and is separated from the bottom wire in the region of the sheet transfer box, wherein the improvement comprises:
the path of the bottom forming wire upstream of the lead-in-foil cover and downstream of the sheet transfer box lies in a substantially horizontal plane;
a blank, convexly curved, stationary secondary trailing cover having a top wire engaging surface and a leading edge, said cover being disposed within, and pressed into, the top wire intermediate the lead-in-foil cover and sheet transfer box to thereby define a concave upward path for the wires to travel thereover;
primary and secondary autoslices are disposed within the top wire intermediate the lead-in-foil cover and the secondary trailing cover;
a secondary foil cover, having a defined, convexly curved surface, is disposed within, and pressed into, the endless bottom wire intermediate the lead-in-foil cover and secondary trailing cover;
a radius of curvature of the secondary trailing cover is smaller than the radius of curvature of the secondary foil cover surface.
the path of the bottom forming wire upstream of the lead-in-foil cover and downstream of the sheet transfer box lies in a substantially horizontal plane;
a blank, convexly curved, stationary secondary trailing cover having a top wire engaging surface and a leading edge, said cover being disposed within, and pressed into, the top wire intermediate the lead-in-foil cover and sheet transfer box to thereby define a concave upward path for the wires to travel thereover;
primary and secondary autoslices are disposed within the top wire intermediate the lead-in-foil cover and the secondary trailing cover;
a secondary foil cover, having a defined, convexly curved surface, is disposed within, and pressed into, the endless bottom wire intermediate the lead-in-foil cover and secondary trailing cover;
a radius of curvature of the secondary trailing cover is smaller than the radius of curvature of the secondary foil cover surface.
4. A twin wire paper forming machine according to claim 3, further including:
a primary trailing cover disposed within the top wire intermediate the primary and secondary autoslices.
a primary trailing cover disposed within the top wire intermediate the primary and secondary autoslices.
5. A twin wire paper forming machine according to claim 4, wherein:
the surface of the primary trailing cover is convex.
the surface of the primary trailing cover is convex.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8319906 | 1983-07-23 | ||
| GB838319906A GB8319906D0 (en) | 1983-07-23 | 1983-07-23 | Paper forming machines |
| GB8414444 | 1984-06-06 | ||
| GB08414444A GB2143871B (en) | 1983-07-23 | 1984-06-06 | Twin wire paper forming machine |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1240187A true CA1240187A (en) | 1988-08-09 |
Family
ID=26286679
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000458642A Expired CA1240187A (en) | 1983-07-23 | 1984-07-11 | Paper forming machines |
Country Status (12)
| Country | Link |
|---|---|
| EP (1) | EP0136000B1 (en) |
| KR (1) | KR920007941B1 (en) |
| AR (1) | AR231849A1 (en) |
| BR (1) | BR8403628A (en) |
| CA (1) | CA1240187A (en) |
| DE (1) | DE3468457D1 (en) |
| FI (1) | FI842918A (en) |
| GB (1) | GB2143871B (en) |
| IN (1) | IN161884B (en) |
| MX (1) | MX161074A (en) |
| PH (1) | PH25831A (en) |
| PL (1) | PL143034B1 (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6982025B2 (en) | 2000-12-15 | 2006-01-03 | Astenjohnson, Inc. | Adjustable resilient blade support |
| US6984291B2 (en) | 2000-12-15 | 2006-01-10 | Astenjohnson, Inc. | Vacuum box with skimmer blade |
Families Citing this family (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FI851035L (en) * | 1984-05-03 | 1985-11-04 | Beloit Corp | OEVRE FORMNINGSVIRA I EN PAPPERSMASKIN. |
| FI82084C (en) * | 1985-01-28 | 1991-01-10 | Valmet Oy | Upper virus unit |
| GB8710428D0 (en) * | 1987-05-01 | 1987-06-03 | Beloit Corp | Multi-ply web forming apparatus |
| FI77281C (en) * | 1987-06-18 | 1989-02-10 | Valmet Paper Machinery Inc | HYBRIDFORMARE FOER EN PAPPERSMASKIN. |
| FI885606A (en) * | 1988-12-01 | 1990-06-02 | Ahlstroem Valmet | BANFORMNINGSFOERFARANDE OCH ANORDNING. |
| FI98540C (en) * | 1989-05-08 | 1997-07-10 | Valmet Corp | Device for forming a paper or board web of fibrous material |
| EP0455784A4 (en) * | 1989-11-03 | 1992-04-08 | Peter A. Rodriguez | Method and apparatus for recovering pulp solids from whitewater |
| FI82954C (en) * | 1990-04-20 | 1991-05-10 | Valmet Paper Machinery Inc | Device in a paper machine |
| US5468348A (en) * | 1990-07-10 | 1995-11-21 | Beloit Technologies, Inc. | Multi-ply web former and method |
| DE4028126C2 (en) * | 1990-09-05 | 1993-10-14 | Escher Wyss Gmbh | Slot nozzle, in particular for a twin wire former and their use in a twin wire former |
| US5202000A (en) * | 1991-09-30 | 1993-04-13 | Beloit Technologies, Inc. | Saveall apparatus for a twin-wire former |
| DE4219292A1 (en) * | 1992-06-12 | 1993-12-16 | Escher Wyss Gmbh | Twin wire former |
| AT502805B1 (en) * | 2006-01-05 | 2007-06-15 | Andritz Ag Maschf | METHOD AND DEVICE FOR DRAINING A FIBROUS WEB |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB1085592A (en) * | 1964-11-23 | 1967-10-04 | St Annes Board Mill Co Ltd | Dewatering watery pulp to form paper, board or tissue |
| DE3138133C2 (en) * | 1981-09-04 | 1986-03-06 | Sulzer-Escher Wyss GmbH, 7980 Ravensburg | Dewatering unit for Fourdrinier paper machines |
-
1984
- 1984-06-06 GB GB08414444A patent/GB2143871B/en not_active Expired
- 1984-07-11 CA CA000458642A patent/CA1240187A/en not_active Expired
- 1984-07-18 EP EP84304886A patent/EP0136000B1/en not_active Expired
- 1984-07-18 PH PH30997A patent/PH25831A/en unknown
- 1984-07-18 DE DE8484304886T patent/DE3468457D1/en not_active Expired
- 1984-07-19 MX MX202082A patent/MX161074A/en unknown
- 1984-07-20 BR BR8403628A patent/BR8403628A/en not_active IP Right Cessation
- 1984-07-20 PL PL1984248865A patent/PL143034B1/en unknown
- 1984-07-20 IN IN529/MAS/84A patent/IN161884B/en unknown
- 1984-07-20 FI FI842918A patent/FI842918A/en not_active Application Discontinuation
- 1984-07-20 AR AR297296A patent/AR231849A1/en active
- 1984-07-21 KR KR1019840004330A patent/KR920007941B1/en not_active IP Right Cessation
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6982025B2 (en) | 2000-12-15 | 2006-01-03 | Astenjohnson, Inc. | Adjustable resilient blade support |
| US6984291B2 (en) | 2000-12-15 | 2006-01-10 | Astenjohnson, Inc. | Vacuum box with skimmer blade |
Also Published As
| Publication number | Publication date |
|---|---|
| BR8403628A (en) | 1985-07-02 |
| GB2143871A (en) | 1985-02-20 |
| EP0136000B1 (en) | 1988-01-07 |
| KR850001342A (en) | 1985-03-18 |
| IN161884B (en) | 1988-02-13 |
| PH25831A (en) | 1991-11-05 |
| KR920007941B1 (en) | 1992-09-19 |
| GB2143871B (en) | 1986-11-12 |
| AR231849A1 (en) | 1985-03-29 |
| FI842918A0 (en) | 1984-07-20 |
| PL248865A1 (en) | 1985-04-09 |
| EP0136000A3 (en) | 1985-07-10 |
| EP0136000A2 (en) | 1985-04-03 |
| PL143034B1 (en) | 1987-12-31 |
| FI842918A (en) | 1985-01-24 |
| GB8414444D0 (en) | 1984-07-11 |
| DE3468457D1 (en) | 1988-02-11 |
| MX161074A (en) | 1990-07-23 |
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Legal Events
| Date | Code | Title | Description |
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| MKEX | Expiry |