Note: Descriptions are shown in the official language in which they were submitted.
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IMPROVED VENTILATOR FOR OFFSET POCKET
AND METHOD OF VENTILAT'ING SAME
FIELD OF THE INVENTION
The present invention relates to papermaking, and more particularly to the
field of
ventilating or extracting air from a paper machine in order to dry the paper
as it is being
made. More particularly, the invention relates to a method for same and to an
improved
apparatus to be disposed between rows of drying cylinders or rolls in order to
feed dry air
and evacuate moist air during the drying operation of papermaking.
BACKGROUND OF THE INVENTION
Ventilators to be used with paper machines in the process of drying the paper
sheet
as it is being displaced through the paper machine are well known in the art.
For example,
US 4,539,762 (Eskelinen), US 4,881,327 (Hauser), US 5,044,095 (Eivola), US
5,379,526
(Haverinen) all disclose various different models disclosing various
configurations and
dispositions of ventilators to be disposed in pockets. However, none of the
above-quoted
prior art patents discloses a ventilator which meets the requirements to be
met by the present
invention. In particular, none of the above prior art disclose a ventilator
which is adapted to
be used in paper machines having offset pockets. Further, none of the above-
quoted prior
art patents discloses a pocket ventilator which discloses the characteristics
of the present
invention nor discloses the advantages thereof. Finally, none of the above-
quoted prior art
patents are efficient or effective when utilized in a paper machine having
offset pockets.
It is therefore an object of the present invention to provide for an improved
pocket
ventilator.
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It is a further object of the present invention to provide an improved pocket
ventilator
adapted to an environment where offset pockets have been created through the
displacement
of the felt rolls towards the wet end of a paper machine.
It is a further object of the present invention to provide for a more
efficient apparatus
to ventilate offset air pockets of a paper machine.
It is a further object of the present invention to use the naturally occurring
air currents
and flows within an offset pocket in order to enhance the efficiency of the
improved
ventilator of the present invention.
It is a further object of the present invention to provide a method for
ventilating offset
pockets.
SUMMARY OF THE INVENTION
Making paper is increasingly becoming a sophisticated operation involving
massive and very expensive paper machines. These paper machines are
increasingly running
at higher and higher speeds, meaning that their overall efficiency must be
very high, and in
particular, the efficiency of their sub-components must also be very high.
Paper making
requires, inter alia, the drying of a pulp fiber solution by passing said pulp
over a large
number of drying rolls. The operation requires that the paper sheet or web be
supported on
a sheet, felt, wire or other support means and as the web is advanced (i.e. as
it is moved or
entrained) through the paper machine, water is removeci (i.e. evaporated)
therefrom. The
web is advanced from the wet end (i.e. the beginning of the machine) to the
dry end (i.e. the
end of the machine) where, when the paper making process is over, the finished
product (i.e.
the paper) is wound and rolled.
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Paper machines may have a number of configurations. One configuration in
particular
may be that the paper making machine comprise twa or more rows of heated
drying
cylinders or rolls over which the web (i.e. the wet paper in the process of
being dried) is
supported and is made to be in contact with. This contact of the web and the
drying rolls may
be primarily responsible for the drying of the web. Intermediate the two rows
of drying
rolls, there is often located a row of felt rolls, which felt rolls support
the wire as it also
moves through the machine. In order to dry the web, it is desirable that it be
in (direct)
contact with the drying rolls as much as possible. However, at certain
intervals, the web is
supported by the wire as the web passes from one drying roll to the other, as
it is being
advanced through the machine. Traditional drying roll and felt roll
arrangement comprises
the placing of the felt roll intermediate the axis of rotation of the drying
rolls, i.e.
substantially halfway between two adjacent drying rolls. Inherent in the
configuration and
disposition of the drying rolls and felt rolls, is the fact that the web is
unsupported for certain
periods of time, especially as the web advances from a drying roll to the next
drying roll, and
the wire separates from the web to pass over the next felt roll.
However, in order to increase the speed of paper machines and at the same time
reduce the
length of unsupported web, paper machine makers have improved the disposition
and
configuration of the felt rolls by moving the axis of rotation of the felt
rolls backwards, i.e.
towards the wet end of the machine. The resulting effect of moving the felt
rolls backwards
has been the creation of what is known as offset pockets. An offset pocket may
be described,
in part, as the space limited by the felt roll, a dryer roll either above or
below it and the paper
web on both sides of the felt roll. The creation of offset pockets has
resulted in the felt and
the web being in contact longer, thus minimizing the length of unsupported web
as the web
passes between adjacent drying rolls. This improvement in paper machine
technology has,
inter alia, reduced the unsupported draw and minimized. sheet fluttering
problems.
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Unfortunately, this change in felt roll configuration has made the ventilation
of the
pockets (i.e. offset pockets) more difficult, and since one of the fundamental
aspects of
paper making is drying of the web, increased difficulty in ventilating the
offset pockets may
therefore be counter productive to increasing paper machine speeds. The
difficulty created
with the configuration of the offset pocket may be due in part from the
elimination (or
reduction) of the wire (i.e. wire without web joined thereto) upstream of the
felt roll where
heated dry air used to normally be introduced therethrough. With an offset
pocket, the
upstream part of the pocket from a felt roll has a wire to which the web is
joined. Since the
web is substantially impermeable to air, when the web is in contact with the
wire, air cannot
be blown through the wire into the pocket. The result is that it has become
impossible to
blow air through that section of wire where the web is in continuous contact
with the wire,
i.e. upstream from the felt roll. This has resulted in decreased air flow into
the pocket, with
a resultant decrease in the efficiency of the ventilation and drying of the
web.
The changing configuration of the pockets has resulted in that there may only
be one area
through which there may be introduced ventilation air into the pocket, namely
on the dry end
side of the pocket, between the point where the fabric leaves the felt roll
and the point where
the fabric comes into contact with the next following dryer roll.
The geometry of an offset pocket and the natural air currents generated by the
moving web
and wire, as well as the turning of the drying and other rolls are factors
which increase the
dii ficulty in ventilating a pocket. Air introduced in the pocket may have a
natural tendency
to follow the movement of the wire and may therefore be trapped in what is
known as a
closing nip, which is formed at the intersection of the wire and the next
drying cylinder. This
may have a tendency to create a zone of positive air pressure in the space
where the wire and
the drying roll meet. As this zone is in positive (i.e. high) pressure, air
may flow (i.e. readily
flow) through the web, i.e. evacuate the pocket through the fabric at the
closing nip, along
the full width of the pocket. Further, a zone of negative air pressure may be
created at what
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is known as the opening nip, the location where the web leaves the felt roll
on its way to the
next drying roll. Some air (i.e. a small quantity) may therefore evacuate the
pocket at the
opening nip to satisfy the negative pressure created therein. However, these
natural air
currents may not provide an effective ventilation of the pocket as there may
not be an
effective sweep of the pocket, and the air may become entraped therein. The
humidity level
may therefore remain high within the pocket, therefore reducing the drying
capacity of the
machine. However, taking advantage of some of these natural air flows, and
enhancing
them, may aid the improved ventilator of the present invention.
Therefore, in accordance with a general aspect of the present invention, there
may be
provided for a:
ventilator to be used to ventilate an offset pocket of a paper making machine
said paper making machine comprising a row of spaced apart upper drying rolls
and
a row of spaced apart lower drying rolls, and
a row of spaced apart felt rolls disposed intermediate said upper drying rolls
and said lower drying rolls, said felt rcills having their axis of rotation
disposed anterior the midpoint between a pair of adjacent drying rolls,
said paper making machine further comprising a web intermittently carried by a
wire
entrained over said upper drying rolls and over said lower drying rolls,
said ventilator being disposed in an open pocket adjacent said offset pocket,
said
open pocket being bounded by a first drying roll, a first felt roll and a
portion
of the web being carried by the wire from said first drying roll to said first
felt
roll, and a portion of the wire disposed between said first felt roll and a
second
drying roll disposed adjacent said first drying roll, said first and second
drying
rolls being selected from a group comprising said upper drying rolls or said
lower drying rolls,
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said ventilator comprising a ventral face and a dorsal face, said ventral face
comprising at
least one ventral orifice disposed adjacent said wire and said dorsal face
comprising at least
one dorsal orifice disposed adjacent said web being carried by the wire,
wherein said ventral orifice discharges a fluid into the path of the wire such
that said
fluid traverses said wire to the other side thereof and into said offset
pocket, and
wherein said dorsal orifice discharges a fluid in a direction opposite to the
direction
of travel of said portion of the web being carried by the wire.
In accordance with a further aspect of the present invention, there is
provided for:
a ventilator to be used to ventilate an offset pocket of a paper making
machine,
said paper making machine comprising a row of spaced apart upper drying rolls
and
a row of spaced apart lower drying rolls, and
a row of spaced apart felt rolls disposed intermediate said upper drying rolls
and said lower drying rolls, each of said felt rolls having its axis of
rotation
disposed anterior the midpoint between a pair of adjacent upper rolls,
said paper making machine further comprising a web intermittently carried by a
wire
entrained over said upper drying rolls and over said lower drying rolls,
said ventilator being disposed in an open pocket adjacent said offset pocket,
said
open pocket being bounded by a first drying roll, a first felt roll and a
portion
of the web being carried by the wire from said first drying roll to said first
felt
roll, and a portion of the wire disposed between said first felt roll and a
second
drying roll disposed adjacent said first upper drying roll, said first and
second
drying rolls being selected from a group comprising said upper drying rolls or
said lower drying rolls,
said ventilator comprising a ventral face and a dorsal face, said ventral face
comprising at
least one ventral orifice disposed adjacent said wire and said dorsal face
comprising at least
one dorsal orifice disposed adjacent said web being carried by the wire,
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said ventilator further comprising a seal means wherein said seal means
divides said
open pocket into a first volume associated with said ventral orifice and a
second
volume associated with said dorsal orifice,
said first volume being disposed intermediate said ventral face and said wire,
and
said second volume being disposed intermediate said dorsal face and said web
being carried by the wire,
wherein said ventral orifice discharges a fluid into said first volume such
that said
first volume is in positive pressure, causing an air flow from the first
volume into said
offset pocket
and wherein said dorsal orifice discharges a fluid into said second volume
such that a movement of air is caused out of said second volume in the
direction opposite to that of the movement of said portion of the web being
carried by the wire.
Further, there is provided for:
a method of ventilating an offset pocket of a paper making machine through the
use of a
ventilator,
said paper making machine comprising a row of spaced apart upper drying rolls
and
a row of spaced apart lower drying rolls, and
a row of spaced apart felt rolls disposed intermediate said upper drying rolls
and said lower drying rolls, each of said felt rolls having its axis of
rotation
disposed anterior the midpoint between a pair of adjacent upper rolls,
said paper making machine further comprising a web intermittently carried by a
wire
entrained over said upper drying rolls and over said lower drying rolls,
said ventilator being disposed in an open pocket adjacent said offset pocket,
said
open pocket being bounded by a first drying roll, a first felt roll and a
portion
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of the web being carried by the wire from said first drying roll to said first
felt
roll, and a portion of the wire disposed between said first felt roll and a
second
drying roll disposed adjacent said first upper drying roll, said first and
second
drying rolls being selected from a group comprising said upper drying rolls or
said lower drying rolls,
said ventilator comprising a ventral face and a dorsal face, said ventral face
comprising at
least one ventral orifice disposed adjacent said wire and said dorsal face
comprising at least
one dorsal orifice disposed adjacent said web being carried by the wire,
said ventilator further comprising a seal means wherein said seal means
divides said
open pocket into a first volume associated with said ventral orifice and a
second
volume associated with said dorsal orifice,
said first volume being disposed intermediate said ventral face and said wire,
and
said second volume being disposed intermediate said dorsal face and said web
being carried by the wire,
said method comprising the steps of
establishing a positive pressure in said first volurne such that an air flow
is created
from said first volume into said offset pocket
and
producing an air flow in said second volume such that a movement of air is
caused out of the second volume in the direction opposite to that of the
movement of said portion of the web being carried by the wire.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a schematic side elevation view of a section of a paper machine;
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Figure 2 is a close-up schematic side elevation view of a portion of a paper
machine;
Figure 3 is a close-up schematic side elevation view of a part of a paper
machine
indicating some air flows therein;
Figure 4 is a schematic side elevation view of a pocket ventilator.
Figure 5 is a perspective partial view of a ventilator connected to an air
supply duct.
Figure 6 is a sectional view of ventilator along view lines 6-6 of figure 5.
Figure 7 is a close-up view of ventilator in accordance with an additional
aspect of
the present invention .
Figure 8 illustrates an alternative embodiment of ventilator in accordance
with a
further aspect of the present invention.
DETAILED DESCRIPTION OF THE EMBODIMENTS
Figure 1 illustrates a schematic side elevation view of a portion of a paper
machine
1 showing a possible configuration thereof. As illustrated, paper machine 1
comprises a
double row of spaced-apart drying rollers 3 disposed at substantially equal
spacing one from
another, namely upper rollers 3(a), 3(c), 3(e), and lower rollers 3(b), 3(d).
Intermediate each
row of spaced-apart drying rollers 3, there is illustrated a line of felt
rolls 5 disposed within
a triangle formed by the immediate three adjacent drying rollers 3. As
illustrated, the felt
rolls 5 are not disposed in a horizontal line, but may be vertically
staggered. It is understood
that the configuration and disposition of both the drying rolls 3 and felt
rolls 5 may differ
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from that illustrated in figure 1 according to each specific configuration of
a particular paper
machine .
The paper machine 1 illustrated in figure 1 has as a purpose the drying of
paper (i.e.
web 9), which process involved, inter alia, the drying of the wet web 9 which
is introduced
at the wet end 15 of the paper machine (not shown). The unfinished paper
(called the web
9) is advanced through the paper machine 1 and dried, until eventually dry
paper is produced
at the dry end 17 of the machine (not shown). Thus, as may be understood, a
tremendous
amount of moisture needs to be evaporated, (i.e. dried) from the pulp fiber
solution or web
9, in order to leave behind the finished paper product. The web 9 is unstable,
particularly at
the wet end of the machine, and due to its wet and weak form, requires to be
supported by
a wire (or felt) 7 as it is being advanced about the plurality of drying
rollers 3, and as it is
progressively being dried out. For example, the web 9 is supported by the wire
7 between
drying ro113(f) and felt roll 5(a), between drying roll 3(a) and felt
rol15(b), etc.... and when
the web is supported by the wire, it is designated by reference number 11.
However, the web
9 is at times unsupported by the wire 7, for example between felt roll 5(a)
and drying roll
3(a), between felt roll 5(b) and drying roll 3(b) etc... When unsupported, the
web 9 may be
designated as unsupported draw 10.
The configuration and disposition of the drying rolls 3 and felt rolls 5
illustrated in
figure 1 creates what is known as an offset pocket 20, 22 identified with the
cross-hatching
as shown in figure 1. The offset pockets 20, 22 may be characterized by the
axis of rotation
of the felt roll 5(a), 5(b) having been displaced backwards towards the wet
end 15 of the
paper machine 1. This offset is illustrated by distance 4 from the axis of
rotation of the
drying roller 3 located immediately below felt roll 5. Traditional felt roll
and drying roll
arrangements may have had the axis of rotation of a felt roll be in vertical
alignment with
the axis of rotation of a drying roll.
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As illustrated in figure 1, the configuration and disposition of a drying
rol13(a) and
of an adjacent felt roll 5(a) defines offset pockets which may be either top
pockets 20 or
bottom pockets 22. Each of these pockets may be described as a space bounded
by, in the
case of top pocket 20, the felt roll 5(b), web 9, drying roll 3(b), wire 7 and
web 9. Top
pocket 20 is identified with cross hatching. In the case of the bottom pocket
22, the offset
pocket 22 may be described as the space limited by web 9, drying roll 3(a),
felt roll 5(a),
web supporting wire 11, and web 9. As may be understood, each of the felt
rolls 5, and each
of the drying roll 3 disposed either above or below, may define either a top
pocket 20 or a
bottom pocket 22.
Thus, as illustrated, the web 9 is at times unsupported as it travels between
a felt roll
5(c) and the next drying roll 3(c), and this unsupported draw is identified by
reference
number 10. As illustrated in figure 1, the direction of movement of the web 9
and wire 7
is illustrated by motion arrow 12 and may generally be described as being from
left to right.
The displacement of the felt rolls 5 towards the wet er.id 15 of the paper
machine 1 has
resulted in reducing the length of the unsupported web 10. For example, the
distance
between a felt roll 5(d) and a preceding drying roll 3(c), comprises the web 9
being
supported by the wire 7 as illustrated by reference number 11 for at least
part of the distance
between a drying rol13(c) and the next drying roll 3(d).
Figure 2 illustrates a close-up schematic side elevation view of a paper
machine 1.
The offset pocket is identified by cross hatched area identified by reference
number 20, and
is bounded on the top by the web 9(a), a felt ro115, and the wire 7, and on
the bottom by a
drying rol13 and web 9(b). Offset pocket 20 may be sealed (i.e. air
impermeable) on its
perimeter (save for the part bounded by the wire 7, which is air permeable),
but is open at
both lateral ends. As may be understood, ventilating an offset pocket 20 as
illustrated may
prove problematic, as it is bounded on one side by the wire supported web 11
which, since
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it is made of paper (i.e. wet paper), is impermeable to air. This part of the
pocket is indicated
by reference number 16. Further, unsupported web 9(a) is also impermeable to
air, which
distance is indicated by reference number 10. Further, the felt roll 5 and the
drying roll 3
are non porous, and in any event, evacuating air therethrough may be
completely
impractical. The only aspect of the offset pocket 20 which may therefore be
readily
ventilated is the wire side 7 also known as open wire draw, illustrated by
reference number
18.
Figure 3 is a close-up schematic side elevation view of a portion of a paper
machine
indicating some of the air flow patterns which may occur within an offset
pocket 20. As
illustrated, web 9 is made to advance in the direction of motion arrow 12
through the
rotation of the drying rolls 3 in the direction of motion arrows 19 and 21. As
may be
understood, the velocity at which the web may be made to be displaced through
the paper
machine 1 may be in the range of 2,000 to 6,000 feet per minute, which high
speed
displacement may create some significant air flows in the offset pocket 20,
especially at the
higher range of such speeds. In particular, in the area of the offset pocket
20 air currents
may be created such that air is displaced generally in the direction of motion
arrows 35, i.e.
towards the upper right-hand drying roller 3. Thus, since web 9b is generally
impermeable
to air, air displaced upwardly in the direction of motion arrows 35 will have
a tendency to
want to pass through open web draw 7 generally in the directions of motion
arrows 37.
Further, the accumulation of air in the upper right-hand corner between open
web draw 7
and drying roller 3 may cause what is known as a closing nip area 33 which may
generally
be a one of positive air pressure. Alternatively, the area where the open web
draw 7 pulls
away from felt roller 5b may be known as an opening nip area 31, and may be an
area
which may be generally under negative pressure. As is understood, air may tend
to flow
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from an area ofpositive pressure to negative pressure, which may explain the
motion arrows
37.
In order to enhance or facilitate what may be the natural flow of air in the
offset
pocket 20 as illustrated in figure 3, and therefore promote the ventilation of
offset pocket
21, a pocket ventilator 41 may be disposed in the area 28 above the offset
pocket 20 as
illustrated in figure 4. It is understood that the configuration of figure 4
wherein a pocket
ventilator 41 is shown disposed adjacent an upper offset pocket may be
replicated with
appropriate modifications if necessary to provide for a ventilator in a
corresponding area
adjacent a lower offset pocket 22, i.e. for example, by flipping the
ventilator 41 about a
horizontal axis. Pocket ventilator 41 is illustrated as a cross-section of a
ventilator which
may be disposed to cover the whole width of a paper machine, i.e. from one
lateral side and
to the opposed lateral side-end thereof. Alternatively, the pocket ventilator
41 may comprise
a series of distinct and discreet boxes spaced along the width of a paper
machine, each of
which may be individually connected to a fluid source (i.e., for example,
air), or each being
connected to the other and ultimately connected to a single fluid source. The
structure of the
ventilator 41 may have an elongated and hollow sheet metal structure, and
extend along the
entire length of the drying rolls (i.e. drying cylinders) 3, in other words,
having a length
corresponding substantially to the width of the paper machine. Ventilator 41
may be
constructed from a variety of different materials, such as galvanized steel,
stainless steel,
painted carbon steel, aluminum, or any combination of these or other material.
As may be
understood, the configuration and disposition of the ventilator 41 within area
28 may be
modified from that shown in figure 4 in order to suit the particular design of
a given paper
machine. In particular, the size of the ventilator may be modified, such that
it may not
occupy as much space within area 28.
As may be understood, the ventilator 41, in accordance with a particular
embodiment of the
present invention may best be described as being configured and disposed to
take advantage
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of the naturally occurring air currents in the offset pocket 20, and by
introducing air therein
at appropriate locations, in order to enhance, assist and accelerate said air
currents to
ultimately improve the ventilation of the pocket 20. Further, the ventilator
41 may also be
configured and disposed to enhance natural air flows within space 28 i.e. open
pocket 28.
Closing nip area 33 may be under positive or high (i.e. relatively higher)
pressure than the
air found elsewhere in the offset pocket 20. This zone of positive air
pressure may therefore
cause the displacement or movement of air through the wire 7 as air under
positive or higher
pressure may tend to flow to an adjacent area of lower air pressure. This air
movement may
be illustrated by motion arrow 37. The evacuation of air at this closing nip
point 33 may
therefore be increased, enhanced or aided by increasing the pressure of the
air which may
accumulate at the closing nip point 33 . This may be accomplished by the
introduction by the
ventilator 41 of additional air into the upper offset pocket 20, as indicated
by arrows 34. This
may be accomplished by discharging air from the ventilator 41 at a location
adjacent to the
wire 7, and by forcing said air through wire 7 as indicated by motion arrow
34. Once this air
has traversed the wire 7, some of this air may move upwardly, as indicated by
motion arrow
35, and through increase volume and flow, accumulate in the closing nip area
33 and
increase the air pressure therein.
While the above described action may be visualized as being accomplished
through a forced
flow of air across wire 7, this objective may also be seen as being
accomplished through the
creation of an air pressure differential or gradient across wire 7. As air
will flow from an
area of higher (i.e. positive) pressure to an area of lower pressure, to
increase air flow into
offset pocket 20, one may create such a pressure differential, such as for
example, by
increasing the air pressure on the ventilator 41 side of the wire 7. As may be
seen, the
discharge of air from ventilator 41 in a volume disposed between the
ventilator 41 and the
wire 7 adjacent thereto will cause air pressure to increase in this volume 40.
This may be
especially true if the volume is bounded by seal means to contain said volume
of positive
pressure, as illustrated in figure 8.
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Similarly, as explained above, the opening nip area 31 may generally be an
area of negative
air pressure. Said area of negative air pressure may therefore have a tendency
to draw
adjacent air which may be at a higher pressure, and for example, may promote
the movement
of air from the other side of the wire 7 as illustrated by motion arrows 36,
into the opening
nip area 31. Thus the introduction of air into offset pocket 20 as identified
by motion arrows
34, may increase the pressure differential between the opening nip area 3 1
pressure and the
pressure of the offset pocket, therefore promoting air flow through the wire 7
adjacent the
opening nip area 31. This enhanced air flow may be indicated by motion arrow
39. However,
the increased amount of air under ventilator 41 (as in(licated by motion arrow
39) may
eventually be counter productive, unless evacuated. To effect this, the
ventilator may be
provided with an additional air exhaust, which may create an air flow as
indicated by motion
arrow 42, which may enhance the movement of air as indicated by motion arrow
39
upwardly out of the area 28. Thus as may be understood, air flow 42 may create
an area of
relative higher pressure indicated by reference number 43, which may cause or
induce a flow
of air from the area of relative lower pressure 44. The result may be that air
is caused to be
evacuated from area 28, i.e. open pocket 28.
Thus as illustrated, the ventilator 41 in accordance with the present
invention may take
advantage of the naturally occurring air currents and may accentuate or
increase the naturally
occurring air pressure differentials in order to enhance air movement and
increase
evacuation of air out of both the offset pocket 20 and the area 28. As may be
understood,
the expression 'wire' 7 may comprise a felt, synthetic or otherwise, wire, or
any other carrier
which may be configured or designed to carry the web 9., but which at the
present location
does not carry such a web. Further, the expression 'web being carried by the
wire' may be
understood to mean the portion of the web which may be carried by the wire,
and which may
be illustrated by reference number 11.
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Figure 5 is a perspective partial view of an air ventilator in accordance with
an
embodiment of the present invention. Ventilator 41 is illustrated as
comprising a ventral
face 50 and a dorsal face 52, wherein in accordance with a given embodiment,
the ventral
face 50 may be disposed towards the dry end 17 of the machine (not shown) and
the dorsal
face may be oriented towards the wet end 15 of the paper machine (not shown).
Although
the ventilator 41 is shown disposed in this manner in order to be disposed in
area 28 above
offset pocket 20 (as illustrated in figure 4), it is understood that the
ventral face 50 and
dorsal face 52 may be oriented in a different position than that illustrated
in figure 5, for
example in an inverted position, the whole in accordance with the
configuration ofthe offset
pocket 20, which may be a function of the configuration of the paper machine
(not shown).
Further, the bottom offset pocket 22 as illustrated in figure 1 may require a
ventilator 41
which may have a disposition which is inverted from the configuration shown in
the figure
5, i.e. wherein ventral face 50 may still be oriented towards the dry end 17
of the machine.
As illustrated in figure 5, the ventilator 41 may be configured to comprise a
unitary,
i.e. one piece ventilator which may be sized to fit within. a paper machine
and disposed to
occupy the whole lateral width of area 28 from one lateral side of the paper
machine to the
other. Alternatively, ventilator 41 may be configured and disposed in a
different manner
as illustrated in figure 5, and may in fact comprise two separate ventilators
41, one of which
may be disposed in area 28 from the right end of the paper machine towards the
centre
thereof, and a second ventilator 41 may be disposed within area 28 from the
left side of the
paper machine and towards the other ventilator 41.
As illustrated in figure 5, ventilator 41 is shown to be connected to a pipe,
ducting,
or other fluid communications means 45. Motion arrow 47 indicates the
direction of a fluid,
for example, air which may be pumped, pushed or otherwise introduced into said
tubing 45
to be distributed inside ventilator 41. Thus, the introduction of fluid into
ventilator 41 may
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CA 02322112 2000-10-03
cause the inside of the ventilator 41 to be under positive pressure. Although
ambiant air
(i.e., for example heated air or heated ambiant air) is the: most likely fluid
to be introduced
into the duct 45 and ventilator 41, it is understood that any other fluid,
such as any other gas,
may be introduced therein, or in addition to the ambiant air, in order to meet
operational
constraints.
Figure 6 illustrates a sectional view along view lines 6-6 of figure 5. As
illustrated,
ventilator 41 may comprise a ventral face 50 and a dorsal face 52. The inside
volume of
ventilator 41 may be divided into a number of chambers, and as illustrated in
figure 6,
baffles 66 and 64 divide the inside of ventilator 41 into three chambers 53,
54 and 56. As
illustrated, ventilator 41 comprises on its ventral face 50 two openings or
orifices 58 and 60.
Fluid (such as air) provided by duct 45 may be introduced into the inside
volume of
ventilator 41 in any number of ways, and may, for example, be introduced first
into chamber
53 for distribution into chambers 54 and 56 through a series ofperforations 55
and 57 which
may be made in baffle 66. Alternatively, duct 45 may provide fluid into the
ventilator 41
directly into volumes 56 and 54, or alternatively into only one of them in
which case a series
of additional orifices may be required in baffle 64 (not shown) or other
appropriate fluid
communications means provided. As may be understood, the supply of air into
the inside
of ventilator 41 may therefore be accomplished in any variety of ways.
Orifices or openings 58 and 60 may be oriented with respect to ventral face 50
such
that a stream of air 70 and 72 being forced therethrough rnay intersect wire
11 (as shown in
figure 4) at substantially right angles thereto. As a result, the spacial
orientation ofventilator
41 within area 28 may therefore not be exactly as illustrated in figure 4.
Although illustrated
figures 4 and 7 as intersecting the wire 11 at right angles, it is understood
that air streams
70 and 72 may not necessarily do so, and may therefore intersect wire 11 at
any other
required or desired angle. Further, as illustrated, air streams 70 and 72 are
substantially
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CA 02322112 2000-10-03
parallel one with the other, although it is understood that the orientation of
the streams may
be different such that the streams may be convergent or divergent. It may be
further
understood that additional orifices may be provided for on ventral face 50,
for example in
volume 53. Alternatively, the orifices may only be found on ventral face 50
opposite
volume 53. As best illustrated in figure 5, the orifice 58 and 60 are shown to
be distinct,
spaced apart openings, although it is understood that orifices 58 and/or 60
may be a slot
extending the length of the ventilator 41, or comprise a number of smaller
slots, or any other
combination of required or desired openings.
Ventilator 41 may also comprise a third orifice 62 from which a third air
stream 74
may be ejected, from volume 56. As may be seen, orifice 62 may be oriented in
such a
manner that air stream 74 may exit ventilator 41 at a pronounced upward angle.
It is
understood that the location of orifice 62 may alternatively be found on any
position of
dorsal face 52, and there may be additional orifices on dorsal face 52 than
illustrated in
figure 6.
Figure 7 is a close-up of ventilator 41 disposed in area 28 above offset
pocket 20 as
illustrated in figures 1 through 4. In this embodiment, ventilator 41
comprises a seal means
78 which as illustrated may be disposed adjacent its lowermost portion.
Further, as may be
understood, if a ventilator 41 is to be used in a lower offset pocket 22 as
illustrated in figure
1, its seal means 78 would inversely be disposed as illustrated in figure 7.
Further, even
though seal means 78 is shown as projecting from ventilator 41 at
substantially its lowermost
portion, it may be understood that seal means 78 may be disposed at another
location along
ventral face 50, i.e. for example, halfway up ventral face 50.
Seal means 78 may divide area 28 into two separate and distinct zones or
volumes,
namely a first volume 80 identified by cross hatching and second volume 82. As
illustrated
1 g
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in figure 7, seal means 78 may substantially act as a barrier or seal between
first and second
volumes 80 and 82, and may therefore be disposed along the whole length of
ventilator 41.
Further, the size of the seal means 78 may be such that it may be disposed as
close as
possible to the wire 7 in order that the seal may be as effective as possible
without risking
damage thereto. As may be understood, the purpose of seal means 82 may be to
create first
volume 80, which first volume 80 may then be made to be under positive
pressure (i.e.
higher pressure) by the introduction therein of air from air streams 70 and
72. The creation
of the first volume 80 which is under positive pressure, or the introduction
of air streams
(immediately) adjacent to the wire, or maybe a combination of the two, may
cause a volume
of air to traverse wire 7.
Figure 8 illustrates an alternative embodiment of ventilator 41 in accordance
with a further
aspect of the present invention. As shown, ventilator 41 comprises a seal
means, which as
illustrated, comprises a lower seal tongue 84 which is disposed removed from
the lower
portion of ventilator 41 as illustrated in figure 7. Further, an upper seal
tongue 86 is shown
spaced apart from lower seal tongue 84. In between, there is located air
streams 70 and 72
which are forced out of orifices 58 and 60 as per figure 5. As may be
understood, first
volume 80 may be better closed off by the presence of a seal means comprising
two or more
seal tongues. In accordance with a further embodiment, the upper seal tongue
86 may be
disposed on the ventral face, at or substantially at the uppermost extremity
of ventral face
50.
The particular embodiment shown herein are by way of example only, and are for
purposes
of illustrative discussion of the many possible embodiments of the present
invention. They
are presented for illustration and easy reference. The illustrations and
description should not
be interpreted in any limiting manner. As will be apparent to one skilled in
the art, further
embodiments may also be comprised within the scope of'the present invention.
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