CA2322112C - Improved ventilator for offset pocket and method of ventilating same - Google Patents
Improved ventilator for offset pocket and method of ventilating same Download PDFInfo
- Publication number
- CA2322112C CA2322112C CA 2322112 CA2322112A CA2322112C CA 2322112 C CA2322112 C CA 2322112C CA 2322112 CA2322112 CA 2322112 CA 2322112 A CA2322112 A CA 2322112A CA 2322112 C CA2322112 C CA 2322112C
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- Prior art keywords
- ventilator
- wire
- ventral
- orifice
- rolls
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- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
- D21F5/00—Dryer section of machines for making continuous webs of paper
- D21F5/02—Drying on cylinders
- D21F5/04—Drying on cylinders on two or more drying cylinders
- D21F5/042—Drying on cylinders on two or more drying cylinders in combination with suction or blowing devices
- D21F5/046—Drying on cylinders on two or more drying cylinders in combination with suction or blowing devices using pocket ventilation systems
Abstract
The ventilator is to be disposed between rows of drying cylinders in papermaking machines in order to feed dry air and evacuate moist air during the drying operation of papermaking. A method of ventilating an offset pocket is also disclosed. The ventilator includes a ventral face and a dorsal face. The ventral face comprises at least one ventral orifice disposed adjacent to the wire and the dorsal face comprises at least one dorsal orifice disposed adjacent to the web being carried by the wire. The ventral orifice discharges air into the path of the wire such that the fluid traverses the wire to the other side and then goes into the offset pocket. The dorsal orifice discharges air in a direction opposite the direction of travel of the portion of the web being carried by the wire. The ventilator improves the ventilation of offset pockets.
Description
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.
McC'arthy Tetrault MTL LAW 4470809 / v. I
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.
Mc( :'arthy Tetrault A1TL LAW #4 70809 / v. 1 2 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.
A1c('arthy Tetrault ti1TL LAW #470809 / v. 1 3 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 McCarthy Tetrault Nf7L LAW #470809/v. 1 4 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, McCarthy Tetrault MTL LAW 4470809/v. 1 5 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, McCarthy Tetrault MTL_LAW #4710809 / v. l 6 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 A1cC'arthy Tetrault MTL LAW #470809/v. 1 7 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;
Mc('arthy Tetrault MTL LAW 4470809 / v. 1 8 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 Mc('arthy Tetrault MTL_LAW 9470809/v. 1 9 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.
McCarthy Tetrault MTL LAW #470809 / v. 1 10 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 Mc('arthy Tetrault MTL LAW #470809 / v. I 11 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 AIcC'arthy Tetrault MTL LAW #470809 / n. 1 12 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 McCarthy Tetrault MTL_LAW #470809 / v. 1 13 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.
Mc('arthy Tetrault MTL LAW #4 70809 / v. 1 14 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 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.
McCarthy Tetrault MTL_LAW #470809 / v. 1 15 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 Mc('arthy Tetrault MTL_LAW #470809 / v. 1 16 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 McC'arthy Tetrault MTL LAW #470809 / v. 1 17 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 McC"arthy Tetrault MTL_LAW #470809 / v. 1 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.
McC-'arthy Tetrault MTL_LAW #470809 / r. 1 19
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.
McC'arthy Tetrault MTL LAW 4470809 / v. I
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.
Mc( :'arthy Tetrault A1TL LAW #4 70809 / v. 1 2 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.
A1c('arthy Tetrault ti1TL LAW #470809 / v. 1 3 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 McCarthy Tetrault Nf7L LAW #470809/v. 1 4 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, McCarthy Tetrault MTL LAW 4470809/v. 1 5 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, McCarthy Tetrault MTL_LAW #4710809 / v. l 6 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 A1cC'arthy Tetrault MTL LAW #470809/v. 1 7 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;
Mc('arthy Tetrault MTL LAW 4470809 / v. 1 8 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 Mc('arthy Tetrault MTL_LAW 9470809/v. 1 9 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.
McCarthy Tetrault MTL LAW #470809 / v. 1 10 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 Mc('arthy Tetrault MTL LAW #470809 / v. I 11 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 AIcC'arthy Tetrault MTL LAW #470809 / n. 1 12 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 McCarthy Tetrault MTL_LAW #470809 / v. 1 13 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.
Mc('arthy Tetrault MTL LAW #4 70809 / v. 1 14 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 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.
McCarthy Tetrault MTL_LAW #470809 / v. 1 15 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 Mc('arthy Tetrault MTL_LAW #470809 / v. 1 16 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 McC'arthy Tetrault MTL LAW #470809 / v. 1 17 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 McC"arthy Tetrault MTL_LAW #470809 / v. 1 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.
McC-'arthy Tetrault MTL_LAW #470809 / r. 1 19
Claims (28)
1. 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 rolls 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, 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.
2. The ventilator of claim 1 wherein said fluid is air.
3. The ventilator of claim 1 wherein said ventral orifice is configured to be continuous along the length of said ventral face.
4. The ventilator of claim 1 wherein said ventral orifice comprises a series of spaced apart openings therein.
5. The ventilator of claim 4 wherein said spaced apart openings are regularly spaced apart along said ventral face.
6. The ventilator of claim 1 wherein said dorsal orifice is configured to be continuous along the length of said dorsal face.
7. The ventilator of claim 1 wherein said dorsal orifice comprises a series of spaced apart openings therein.
8. The ventilator of claim 7 wherein said spaced apart openings are regularly spaced apart along said dorsal face.
9. The ventilator of claim 1 wherein said ventral orifice is disposed on said ventral face adjacent said felt roll.
10. The ventilator of claim 1 wherein said dorsal orifice is disposed on said dorsal face adjacent said felt roll.
11. The ventilator of claim 1 wherein said ventilator is connected to a fluid supply source which establishes a positive air pressure within said ventilator.
12. The ventilator of claim 1 wherein said ventilator comprises a seal means projecting outwardly from said ventilator between said ventral face and said wire.
13. The ventilator of claim 12 wherein said seal means is disposed adjacent said felt roll.
14. The ventilator of claim 12 wherein said seal means comprises a first seal tongue disposed adjacent said felt roll and a second seal tongue disposed above said ventral orifice.
15. 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, 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.
16. The ventilator of claim l5wherein said fluid is air.
17. The ventilator of claim 15 wherein said ventral orifice is configured to be continuous along the length of said ventral face.
18. The ventilator of claim 15 wherein said ventral orifice comprises a series of spaced apart openings therein.
19. The ventilator of claim 18 wherein said spaced apart openings are regularly spaced apart along said ventral face.
20. The ventilator of claim 15 wherein said dorsal orifice is configured to be continuous along the length of said dorsal face.
21. The ventilator of claim 15 wherein said dorsal orifice comprises a series of spaced apart openings therein.
22. The ventilator of claim 21 wherein said spaced apart openings are regularly spaced apart along said dorsal face.
23. The ventilator of claim 15 wherein said ventral orifice is disposed on said ventral face adjacent said felt roll.
24. The ventilator of claim 15 wherein said dorsal orifice is disposed on said dorsal face adjacent said felt roll.
25. The ventilator of claim 15 wherein said ventilator is connected to a fluid supply source which establishes a positive air pressure within said ventilator.
26. The ventilator of claim 15 wherein said seal means is disposed adjacent said felt roll.
27. The ventilator of claim 26 wherein said seal means comprises a first seal tongue disposed adjacent said felt roll and a second seal tongue disposed above said ventral orifice.
28. 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 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 volume 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.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2322112 CA2322112C (en) | 2000-10-03 | 2000-10-03 | Improved ventilator for offset pocket and method of ventilating same |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA 2322112 CA2322112C (en) | 2000-10-03 | 2000-10-03 | Improved ventilator for offset pocket and method of ventilating same |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2322112A1 CA2322112A1 (en) | 2002-04-03 |
| CA2322112C true CA2322112C (en) | 2007-08-28 |
Family
ID=4167301
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2322112 Expired - Lifetime CA2322112C (en) | 2000-10-03 | 2000-10-03 | Improved ventilator for offset pocket and method of ventilating same |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2322112C (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CA2905562C (en) | 2015-01-30 | 2023-03-28 | Enerquin Air Inc. | A pocket ventilator device and method |
-
2000
- 2000-10-03 CA CA 2322112 patent/CA2322112C/en not_active Expired - Lifetime
Also Published As
| Publication number | Publication date |
|---|---|
| CA2322112A1 (en) | 2002-04-03 |
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| EEER | Examination request | ||
| MKEX | Expiry |
Effective date: 20201005 |