APPARATUS FOR REMOVING FLUID FROM A FIBROUS WEB

DISPOSITIF POUR EXTRAIRE UN LIQUIDE D'UNE BANDE FIBREUSE

English Abstract

An apparatus for removing fluid from a fibrous web (30) in a papermaking
machine having a machine direction and a cross machine direction, the
apparatus comprising a plurality of generally parallel supports (50) extending
in the cross machine direction, the supports being spaced in the machine
direction, the supports having mounted thereon respective blades (70)
extending in the cross machine direction, the blades being spaced in the
machine direction along a convex path for movement of the web over the blades,
each blade (70) being movable relative to the respective support (50) in a
direction perpendicular to the web such that outward movement of the blade
(70) relative to the support (50) presses the blade against the web (30), and
a control system for exerting, on each of the blades (70), a force in the
direction toward the web (30) so as to press the blade against the web, the
control system being operable to vary the force exerted on each of the blades
(70) independent of the force exerted on the remaining blades.

French Abstract

Dispositif pour extraire un liquide d'une bande (30) fibreuse dans une machine de fabrication de papier présentant un sens machine et un sens transversal. Le dispositif comporte une pluralité de supports (50) sensiblement parallèles, disposés dans le sens transversal et espacés dans le sens machine. Ces supports portent des lames (70) respectives orientées dans le sens transversal, ces lames (70) étant espacées dans le sens machine le long d'une trajectoire convexe pour permettre à la bande de défiler par dessus les lames. Chaque lame (70) est mobile par rapport au support (50) respectif dans une direction perpendiculaire à la bande, de façon que le mouvement de la lame vers l'extérieur par rapport au support (50) presse la lame contre la bande (30). Le dispositif comprend en outre un système de commande pour imprimer à chacune des lames (70) une force en direction de la bande (30) ayant pour effet de presser la lame conte la bande, ce système de commande permettant de faire varier la force exercée sur chacune des lames (70) indépendamment de la force exercée sur les autres lames.

Claims

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WHAT IS CLAIMED IS:
1. An apparatus for removing fluid from a fibrous web in a
papermaking machine having a machine direction and a cross machine
direction, the apparatus comprising
a base,
a plurality of generally parallel supports mounted on the base, the
supports extending in the cross machine direction and being
spaced in the machine direction, the supports having mounted
thereon respective blades extending in the cross machine
direction, the blades being spaced in the machine direction
along a convex path for movement of the web over the
blades, each blade being movable relative to the respective
support in a direction perpendicular to the web such that
outward movement of the blade relative to the support
presses the blade against the web, and
a control system for exerting, on each of the blades, a force in the
direction toward the web so as to press the blade against the
web, the control system being operable to vary the force
exerted on each of the blades independent of the force exerted
on the remaining blades.
2. An apparatus as set forth in claim 1 wherein each of the
supports is generally T-shaped in cross-section, each of the supports having
therein an outwardly opening recess extending in the cross machine
direction, and each of the supports including opposed flanges extending in
the machine direction on opposite sides of the recess, and wherein each of
the blades is mounted on the respective support such that the flanges limit
movement of the blade relative to the support in the direction perpendicular
to the web.

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3. An apparatus as set forth in claim 2 wherein each of the
blades is secured to a respective blade base which extends in the cross
machine direction and which is generally C-shaped in cross-section, the
blade base having therein an inwardly opening channel receiving the flanges
of the respective support.
4. An apparatus as set forth in claim 3 wherein each blade has a
length in the cross machine direction, wherein each blade base channel and
the respective support recess define a variable volume chamber extending
substantially the entire length of the blade, the chamber having a volume
that changes in response to movement of the blade toward and away from
the web, wherein the control system includes, in each chamber, a
respective flexible conduit extending substantially the entire length of the
blade, the conduit having a closed end and an opposite open end, and
wherein the control system also includes a source of variable pressure
connected to the open end of each conduit, the control system being
operable to vary the pressure in each of the conduits independent of the
pressure in the remaining conduits.
5. An apparatus as set forth in claim 1 wherein each blade and
the respective support define a variable volume chamber having a volume
that changes in response to movement of the blade toward and away from
the web, and wherein the control system is operable to vary the pressure in
the chamber.
6. An apparatus as set forth in claim 5 wherein the force exerted
on the blade increases in response to an increase in the pressure in the
chamber.

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7. An apparatus as set forth in claim 6 wherein the control
system includes; in each chamber, a respective flexible conduit, and
wherein the control system varies the pressure inside the conduit to vary
the pressure in the respective chamber.
8. An apparatus as set forth in claim 7 wherein each of the
conduits has a closed end and an opposite open end, and wherein the
control system also includes a source of variable pressure connected to the
open end of each conduit, the control system being operable to vary the
pressure in each of the conduits independent of the pressure in the
remaining conduits.
9. An apparatus as set forth in claim 1 wherein each blade is
ceramic.
10. An apparatus as set forth in claim 1 wherein adjacent blades
define therebetween spaces, wherein fluid removed from the web by the
blades flows into the spaces, and wherein the apparatus further comprises
a vacuum system for removing fluid from the spaces.
11. An apparatus as set forth in claim 1 wherein the blades face
generally downwardly such that the web passes beneath the blades.
12. A papermaking machine having a machine direction and a
cross machine direction, the machine comprising
a frame,
inner and outer fabrics for carrying a fibrous web therebetween, the
fabrics being supported on the frame for movement in the
machine direction, and

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an apparatus for removing fluid from the web, the apparatus being
supported by the frame, and the apparatus including a plurality
of generally parallel supports extending in the cross machine
direction, the supports being spaced in the machine direction,
the supports having mounted thereon respective blades
extending in the cross machine direction, the blades being
spaced in the machine direction along a convex path for
movement of the fabrics and the web over the blades, with
the inner fabric between the web and the blades, each blade
being movable relative to the respective support in a direction
perpendicular to the web such that outward movement of the
blade relative to the support presses the blade against the
web, and the apparatus also including a control system for
exerting, on each of the blades, a force in the direction toward
the web so as to press the blade against the web, the control
system being operable to vary the force exerted on each of the
blades independent of the force exerted on the remaining
blades.
13. A machine as set forth in claim 12 wherein each of the
supports is generally T-shaped in cross-section, each of the supports having
therein an outwardly opening recess extending in the cross machine
direction, and each of the supports including opposed flanges extending in
the machine direction on opposite sides of the recess, and wherein each of
the blades is mounted on the respective support such that the flanges limit
movement of the blade relative to the support in the direction perpendicular
to the web.
14. A machine as set forth in claim 13 wherein each of the blades
is secured to a respective blade base which extends in the cross machine

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direction and which is generally C-shaped in cross-section, the blade base
having therein an inwardly opening channel receiving the flanges of the
respective support.
15. An apparatus as set forth in claim 14 wherein each blade has
a length in the cross machine direction, wherein each blade base channel
and the respective support recess define a variable volume chamber
extending substantially the entire length of the blade, the chamber having a
volume that changes in response to movement of the blade toward and
away from the web, wherein the control system includes, in each chamber,
a respective flexible conduit extending substantially the entire length of the
blade, the conduit having a closed end and an opposite open end, and
wherein the control system also includes a source of variable pressure
connected to the open end of each conduit, the control system being
operable to vary the pressure in each of the conduits independent of the
pressure in the remaining conduits.
16. A machine as set forth in claim 12 wherein each blade is
ceramic.
17. A machine as set forth in claim 12 wherein adjacent blades
define therebetween spaces, wherein fluid removed from the web by the
blades flows into the spaces, and wherein the apparatus further comprises
a vacuum system for removing fluid from the spaces.
18. A machine as set forth in claim 12 wherein the blades face
generally downwardly such that the web passes beneath the blades.

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19. A curved inverted vacuum apparatus for removing fluid from a
fibrous web in a papermaking machine having a machine direction and a
cross machine direction, the apparatus comprising
a plurality of generally parallel supports extending in the cross
machine direction, the supports being spaced in the machine
direction, each of the supports being generally T-shaped in
cross-section, each of the supports having therein an
outwardly opening recess extending in the cross machine
direction, and each of the supports including opposed flanges
extending in the machine direction on opposite sides of the
recess, the supports having mounted thereon respective
blades extending in the cross machine direction, the blades
being spaced in the machine direction along a convex path for
movement of the web over the blades, the blades facing
generally downwardly such that the web passes beneath the
blades, adjacent blades defining therebetween spaces so that
fluid removed from the web by the blades flows into the
spaces, each blade having a length in the cross machine
direction and being movable relative to the respective support
in a direction perpendicular to the web such that outward
movement of the blade relative to the support presses the
blade against the web, each of the blades being secured to a
respective blade base which extends in the cross machine
direction and which is generally C-shaped in cross-section, the
blade base having therein an inwardly opening channel
receiving the flanges of the respective support such that the
flanges limit movement of the blade relative to the support in
the direction perpendicular to the web, each blade base
channel and the respective support recess defining a variable
volume chamber extending substantially the entire length of

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the blade, the chamber having a volume that changes in
response to movement of the blade toward and away from the
web,
a control system for exerting, on each of the blades, a force in the
direction toward the web so as to press the blade against the
web, the control system being operable to vary the force
exerted on each of the blades independent of the force exerted
on the remaining blades, the control system including, in each
chamber, a respective flexible conduit extending substantially
the entire length of the blade, each of the conduits having a
closed end and an opposite open end, and the control system
including a source of variable pressure connected to the open
end of each conduit, the control system being operable to vary
the pressure in each of the conduits independent of the
pressure in the remaining conduits, and
a vacuum system for removing fluid from the spaces between
adjacent blades.

Description

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1
TITLE:
The invention relates to papermaking machinery, and more
particularly to apparatus for removing fluid from a fibrous web in a
papermaking machine. Still more particularly, the invention relates to a
curved inverted vacuum box.
A known type of twin-wire or twin-fabric former is the Bel Bond
former, which is designed as a retrofit to an existing fourdrinier wire. Bel
Bond is a registered trademark of Beloit Corporation. A Bel Bond former
includes a looped top wire cooperating with the existing fourdrinier or
bottom wire. The Bel Bond former also includes a curved inverted vacuum
box positioned within the loop of the top wire.
The curved inverted vacuum box typically includes a box that is
made from stainless steel or the like and that defines an enclosure
connected to a source of partial vacuum. The box includes a base having a
convex curved surface for guiding the top wire. A plurality of dewatering
blades, usually ceramic, extend in the cross machine direction and are
spaced in the machine direction along the curved surface of the curved
inverted vacuum box. The top and bottom wires sandwich the web, and
dewatering takes place due to tension of both wires, combined with
centrifugal force. The vacuum source urges water upwardly out of the web
through the top wire. A portion of water is removed from the formed web
downwardly through the bottom wire during movement of the wires and
the web over the blades.

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Known prior art curved inverted vacuum boxes do not allow
changing the drainage pressure from one blade to the next so as to allow
experimentation with formation and sheet strength. The invention provides
a curved inverted vacuum box in which each blade is loaded independently,
thus providing the ability to change the drainage pressure at each blade
location. With the consistency of the web or sheet changing along the
curved surface of the curved inverted vacuum box, a controlled induced
drainage curve can be achieved to follow consistency changes along the
curved surface.
More particularly, the invention provides an apparatus for removing
fluid from a fibrous web in a papermaking machine, the apparatus
comprising a plurality of generally parallel supports that extend in the cross
machine direction and that are spaced in the machine direction. Each
support has mounted thereon a respective blade extending in the cross
machine direction. The blades are spaced in the machine direction along a
convex path for movement of the web and, in the preferred embodiment of
the invention, the fabrics, over the blades. Each blade is movable relative
to its respective support in a direction perpendicular to the web such that
outward movement of the blade relative to the support presses the blade
against the web. The apparatus also comprises a control system for
exerting, on each of the blades, a force in the direction toward the web so
as to press the blade against the web. The control system is operable to
vary the force exerted on each of the blades independent of the force
exerted on the remaining blades.
Preferably, the supports are tee bars extending in the cross machine
direction. An air loaded tube is saddled in each tee bar between the tee bar
and the base of the respective blade. When the tube is pressurized, a force

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is exerted, pushing the blade into the fabrics and the web, changing the
drainage pressure at the leading and trailing edges of the blade. A control
panel equipped with gauges, regulators and air lines connected to the
individual air tubes is provided for independent air pressure regulation.
Other features and advantages of the invention will become apparent
to those skilled in the art upon review of the following detailed description,
claims and drawings.
D~R~'TION OF THE DRAWIN ~~
Fig. 1 is a partial side elevational of a papermaking machine
embodying the invention.
Fig. 2 is an enlarged portion of Fig. 1, partially in section.
Fig. 3 is a further enlarged portion of Fig. 2.
Fig. 4 is a partial view taken along line 4-4 in Fig. 3.
0
Before one embodiment of the invention is explained in detail, it is to
be understood that the invention is not limited in its application to the
details of the construction and the arrangements of components set forth in
the following description or illustrated in the drawings. The invention is
capable of other embodiments and of being practiced or being carried out in
various ways. Also, it is understood that the phraseology and terminology
used herein is for the purpose of description and should not be regarded as
limiting.
A papermaking machine 10 embodying the invention is partially
illustrated in Fig. 1. More particularly, the portion of the papermaking
machine 10 illustrated in Fig. 1 is a Bel Bond former 14. As is known in
the art, the Bel Bond former 14 comprises a frame 18 supporting a looped

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bottom fabric or wire 22 moving in the machine direction (from left to right
in Fig. 1 ). A secondary headbox 26 is mounted on the frame 18 above the
bottom fabric 22. A fibrous web 30 (see Fig. 3) is supported on top of and
moves with the bottom fabric 22. Mounted on the frame 18 downstream
of the secondary headbox 26 is (see Fig. 1 ) a looped top fabric or wire 34
positioned such that the web 30 is sandwiched between and moves with
the top fabric 34 and the bottom fabric 22. A curved inverted vacuum box
38 is mounted on the frame 18 within the endless loop of the top fabric
34. The curved inverted vacuum box 38 includes a box 42 defining an
enclosure connected to a source 46 of partial vacuum. The base of the
box 38 has a convex curved surface. The Bel Bond former 14 and the
curved inverted vacuum box 38 as thus far described are conventional and
will not be described in further detail.
As shown in Figs. 2 and 3, a plurality of generally parallel supports
50 are mounted on the curved surface of the box base. The supports 50
extend in the cross machine direction and are spaced in the machine
direction. Preferably, as shown in Fig. 3, the supports 50 are tee bars that
are generally T-shaped in cross-section. Each tee bar 50 has therein an
outwardly or downwardly opening recess 54 extending in the cross
machine direction, and each tee bar 50 includes opposed flanges 58 and 62
extending in the machine direction on opposite sides of the recess 54.
Each tee bar 50 is secured to the box base by a plurality of bolts 66, as
best shown in Figs. 3 and 4.
The tee bars 50 have mounted thereon respective blades 70
extending in the cross machine direction. The blades 70 are preferably
ceramic, as is known in the art. The blades 70 are spaced in the machine
direction along a convex path, as best shown in Fig. 2. The blades 70 face
generally downwardly such that the fabrics 22 and 34 and the web 30

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pass beneath the blades 70, with the blades 70 pressing against the top
fabric 34. Each blade 70 is movable relative to its respective tee bar 50 in
a direction generally perpendicular to the web 30 (vertically in Fig. 3) such
that outward movement of the blade 70 relative to the tee bar 50
5 (downward movement in Fig. 3) presses the blade 70 against the top fabric
34 and the web 30. To this end, each of the blades 70 is secured to a
respective blade base 74 which extends in the cross machine direction and
which is generally C-shaped in cross-section. The blade base 74 has
therein an inwardly or upwardly opening channel 78 receiving the flanges
58 and 62 of the respective tee bar 50 such that the flanges limit vertical
movement of the blade 70 relative to the tee bar 50. Each blade 70 is
movable relative to its tee bar 50 between an uppermost position and a
lowermost position. In Fig. 3, the left-hand blade 70 is shown in its
uppermost position, the right-hand blade 70 is shown in its lowermost
position, and the middle blade 70 is shown in an intermediate position
between the uppermost and lowermost positions. Each blade base channel
78 and the respective tee bar recess 54 define (see Fig. 4) a variable
volume chamber 82 extending substantially the entire length of the blade
70. The chamber 82 has a volume that changes in response to movement
2 0 of the blade 70 toward and away from the web 30. Specifically, the
volume increases in response to downward movement of the blade 70 and
decreases in response to upward movement of the blade 70.
The curved inverted vacuum box 38 also includes (see Fig. 2) a
control system 86 (shown schematically) for exerting, on each of the
blades 70, a downward force so as to press the blade 70 against the
fabrics 22 and 34 and the web 30. The control system 86 is operable to
vary the force exerted on each of the blades 70 independent of the force
exerted on the remaining blades 70. The control system 86 includes, for
each blade 70, a respective flexible conduit or air tube 90 (Figs. 3 and 4)

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saddled in the tee bar 50 between the tee bar 50 and the base 74 of the
blade 70 (i.e., in the variable volume chamber 821. Each tube 90 extends
substantially the entire length of the respective blade 70 and has a closed
end (not shown) and an opposite open end (the left end in Fig. 4). The
control system 86 includes a source 94 of variable pressure connected to
the open end of each tube 90. The control system 8fi also includes (see
Figs. 2 and 4) air lines 98 connected between the pressure source 94 and
the individual air tubes 90. The control system 8fi is operable to vary the
pressure in each of the tubes 90 independent of the pressure in the
remaining tubes 90. In the preferred embodiment of the invention, the
control system 86 includes a control panel (not shown) equipped with
gauges, regulators and a manually adjustable control for each tube 90.
When a tube 90 is pressurized, the tube 90 expands, increasing the volume
of its chamber 82 and pushing the blade 70 downwardly into the fabrics
22 and 34 and the web 30, thereby changing the drainage pressure at the
leading and trailing edges of the blade 70..
Various features of the invention are set forth in the following
claims.

Representative Drawing