CA2025447C - Method and apparatus for reducing vibration in the press section of a papermaking machine - Google Patents
Method and apparatus for reducing vibration in the press section of a papermaking machineInfo
- Publication number
- CA2025447C CA2025447C CA002025447A CA2025447A CA2025447C CA 2025447 C CA2025447 C CA 2025447C CA 002025447 A CA002025447 A CA 002025447A CA 2025447 A CA2025447 A CA 2025447A CA 2025447 C CA2025447 C CA 2025447C
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- CA
- Canada
- Prior art keywords
- felt
- trade line
- orientation
- press section
- roll
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
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- 230000000750 progressive effect Effects 0.000 claims description 9
- 230000003287 optical effect Effects 0.000 claims description 3
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 abstract 2
- 229910052742 iron Inorganic materials 0.000 abstract 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 9
- 238000010586 diagram Methods 0.000 description 5
- 230000007246 mechanism Effects 0.000 description 5
- 230000001351 cycling effect Effects 0.000 description 4
- 230000007547 defect Effects 0.000 description 3
- 230000000694 effects Effects 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 230000008878 coupling Effects 0.000 description 2
- 238000010168 coupling process Methods 0.000 description 2
- 238000005859 coupling reaction Methods 0.000 description 2
- 230000008713 feedback mechanism Effects 0.000 description 2
- 230000003993 interaction Effects 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 239000011148 porous material Substances 0.000 description 2
- TVEXGJYMHHTVKP-UHFFFAOYSA-N 6-oxabicyclo[3.2.1]oct-3-en-7-one Chemical compound C1C2C(=O)OC1C=CC2 TVEXGJYMHHTVKP-UHFFFAOYSA-N 0.000 description 1
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- 230000006866 deterioration Effects 0.000 description 1
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- 238000001035 drying Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000012467 final product Substances 0.000 description 1
- 230000006870 function Effects 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
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- 238000002360 preparation method Methods 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
Classifications
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
- D21F3/00—Press section of machines for making continuous webs of paper
- D21F3/02—Wet presses
- D21F3/04—Arrangements thereof
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
- D21F7/00—Other details of machines for making continuous webs of paper
- D21F7/005—Wire-tensioning devices
Landscapes
- Paper (AREA)
Abstract
Method and apparatus for reducing vibration in the press section of a high speed papermaking machine. The press section has at least one dewatering felt with means such as a trade line for indicating the orientation of the felt in the press section. The press section includes means for adjusting the trade line orientation as the felt cycles in a continous loop through the press section. Barring of the felt, i.e., introduction of thickness variations in the felt by resonant vibrations in the nip, is minimized by progressively altering the trade line orientation as the felt cycles through the press section, the trade line orientation adjustment being accomplished at a rate adequate to iron out bars formed on previous passes and prevent resonant buildup of bars in the felt during operation of the papermaking machine.
Description
FIELD OF THE INVENTION
This invention relates to papermaking machines and more particularly to the press section of high speed papermaking machines and means for reducing vibration in the press section.
BACKGROUND OF THE INVENTION
In papermaking, it is well-known that a paper web is formed from a slurry on a web-forming wire~
and water is removed from the web as it travels through the papermaking machine until the fully dewatered and treated web is wound on a reel at the end of the machine. While this brief statement clearly oversimplifies the papermaking process, it is adequate to direct attention to the press section which is the papermaking machine section of primary interest to the instant invention. More particularly, after the web is formed and partially dewatered in the forming section, the web is passed to a press section where it is carried on dewatering felts and passed between press rolls forming one or more nips. The purpose of the felts and the nips is to remove water from the web, such as by transferring water from the web to the felts.
In conventional papermaking machines, the felts are driven over a plurality of rolls which are mounted in the machine frame to form a path for the felt in a continuous loop. In addition to the aforementioned nips, the rolls which form the loop typically include certain adjustable rolls for adjusting the felt orientation; such adjustable rolls are often configured as seam straighteners or bowed rolls. The press felt itself is in the form of a continuous loop and usually has a trade line which is formed on the felt during its manufacture in such a 23-1~17/mjc way as to relate the pattern of the weave in the felt to the visually perceptible trade line. For example, the trade line is usually painted or otherwise marked on the felt parallel to the orientation of the felt weave so that if the trade line is running square with respect to the press, the operator knows that the weave is uniformly open across the press. It will be appreciated that the felt is usually a woven material, the roll in the press section can tension one part of the felt with respect to others, and the woven material being resilient will deform to accon~odate the new adjustment. The trade line is an indicator of how the weave pattern has accommodated itself to an~ particular press section felt roller adjustment. Thus, if the trade line is bowed or otherwise in a nonlinear orientation, the press operator has information as to which parts of the felt weave are more open or more closed with respect to other parts.
In summary, when the continuous felt loop is installed in a press section, and the felt is run in its continuous loop, the trade line gives an indication of whether the weave pattern is linear across the machine and straight, whether the weave pattern is bowed, or whether one edge is running ahead of the other. The seam straightener is a roll which is journalled such that one end can be advanced or retarded with respect to the other, for the purposes of getting the edges of the felt trade line in the same orientation with respect to each othèr across the press. The bowed roll has a curved axis and can have this axis advanced into or retracted from the felt so as to adjust the center of the felt with respect to its edges thereby to accon~odate for what is called a smile or a frown in the felt.
23-1~7/mjc ~3~ ~L~
Together, the bowed roll and seam straightener are utilized to adjust the orientation of the trade line of the felt with respect to the press section.
Preferably, they adjust the trade line so that it is in a straight line and square with respect to the press, i.e., perpendicular to the machine direction of the press. As a result, the felt weave pattern will be the same orientation across the press (the holes in the weave pattern will not be compressed more in one section than in another due to the fe]t running out of square), and thus the felt will be equally effective across the papermaking machine for removing water f rom the web.
As papermaking machine speeds have increased, vibration has become more and more of a problem.
Excessive vibration tends to introduce unacceptable thickness variations in the formed paper web. One important source of such vibrations is in the nip of the press section, and can result from resonances in the press nip excited by variations in the felt originally created by nip vibrations. When the discontinuities in the felt ~such as bars as will be explained below) arrive at the nip at a frequency which will excite the mechanical system, constructive interference can result, resulting in excessive vibrations and a detrimental effect on web quality.
Thus, if the felt in passing through the nip experiences a change in pressure adequate to cause a slight thickness variation in the felt, on a subsequent pass of the felt through the same nip, that minor thickness variation can again excite the nip to cause a more pronounced vibration. Subsequent cycles can cause a resonant buildup which tends to enhance the thickness variations in the felt, causing a condition known in the trade as barring. The ~3-1~7/m~c MsO81702511 - ~2~
barred felt which continuously passes through the nip, excites the nip, and when the bars are at a predetermined interval for a given press speed and mechanical resonant frequency, the resonances can cause significant thickness variations in the felt, which in turn have an unacceptable effect on the thickness uniformity of the produced web.
It has sometimes been the practice in the past to attempt to deal with felt barring by periodically IsaY on a daily basis) slightly altering the trade line in the press (such as by adjusting the seam straightener) so that the bars created on one day go through the nip on another day out of square and thus do not continue to resonantly excite the apparatus.
However, the felt in its new orientation can create a new set of bars which over the course of the day or until the next adjustment can cause a new set of bars with the accompanying vibration and deterioration of web quality.
SUM~ARY OF THE INVENTION
In view of the foregoing, it is a general aim of the present invention to minimize vibration in the press section of a high speed papermaking machine heretofore caused by resonances carried through the press section by deformations introduced in the felt.
In accomplishing that aim, an object of the present invention is to control the press section in such a way as to minimize vibrations occasioned by resonances excited by the continuous cycling of the press section felts through the nips.
According to a more detailed aspect of the invention, it is an object to reduce resonant vibration in the press section occasioned by resonance excited by the felt, but in such a way as 23-1~7/mjc MB081702~11 ~ ~ 2 ,~
to minimize the effect on the formed web of felt trade line variations.
Other objects and advantages will become apparent from the following detailed description when taken in conjunction with the drawings, in whi~h:
BRIEF DESCRIPTION OF TH~ DRAWINGS
Figure l is a diagrammatic view in perspective illustrating the press section of a papermaking machine;
Fig. 2 is a diagram illustrating the barring phenomenon on a press felt shown in exaggerated cross section;
Fig. 3 is a diagram showing the control elements of the press section of Fig. l adapted for practice of the present invention;
Fig. 4 is a diagram similar to Fig. 3 but in plan view also illustrating the control elements of the press section of Fig. l adapted for practice of the present invention; and Figs. 5 and 6 are a partial schematic diagrams in plan view illustrating progressive adjustment of the trade line orientation for minimizing resonant vibration in the nip of a press section according to the present invention.
While the invention will be described in connection with certain preferred embodiments, there is no intent to limit it to those embodiments. On the contrary, the intent is to cover all alternatives, modifications and equivalents included within the spirit and scope of the invention as defined by the appended claims.
23-1~7/mjc MB081/0~
~2~7 DETAILED DESCRIPTION O~ THE PREFERRED EMBODIMENTS
Turning now to the drawings, Fig. 1 shows schematically and in partial perspective a press section of a papermaking machine. A partly formed and partly dewatered web 20 enters the press section at 21 and passes through several nips 22, 23, 24 where pressure is applied to remove additional water, whereupon the web exits the press section at 25 for passage to downstream equipment such as the dryer.
The illustrated press section includes three press felts 30, 32, 34, each of such felts having an associated roll arrangement 31, 33, 35 about which the associated felt is driven in a continuous loop.
Taking the press felt 30 as exemplary, it is seen that the roll arrangement 31 which defines the loop about which the felt is driven includes a nip roll (or press roll3 40, a plurality of guide rolls 41, a seam straightener roll 42, and a bowed roll 43.
Dryer means 44 are disposed adjacent the felt 30 for removing water from the felt, such as by suction, after the web has left the felt, such that the felt is dried in preparation for again contacting the web ~0 and passing through the nip 22.
The seam straightener roll 42, as will be described in greater detail below, is arranged to tension the felt 30, and also to adjust one end of the felt forward or rearward with respect to the other end, thereby to adjust the orientation of the felt trade line. The trade line for the felt 30 is illustrated at 46 and is seen to be a visible line marked or painted across the felt. In manufacture, the trade line 46 is located on the felt in a predetermined relationship (generally parallel to) the felt weave, such that when the trade line 46 is perpendicular with respect to the path of felt travel 23-1~7/mjc MsO81702511 ~2~
in the press, the felt weave is also square with respect to travel and thus the weave across the felt is open and uniform across the felt. However, when the felt is run with one end leading the other, as illustrated by the trade line 48 on felt 32, the pores of the felt are partly closed due to the skew of the weave. When the felt is run with a smile or a frown, the degree of pore opening varies across the press. In order to correct the trade line orientation from the skewed condition as illustrated at 48, to the squared condition illustrated by trade line 46, the seam straightener roll 42 for the felt in question is adjusted to either retard or advance the forward edge of the felt until the trade line assumes the position of trade line 46, i.e., perpendicular to the direction of travel.
It is also possible for the felt to be tensioned in the press section such that the center is trailing or leading with respect to one or both of the edges, a condition referred to in the trade as smile or frown. The bowed roll 43 has a curvature which can be oriented by an adjustment mechanism such that the curvature or bow can be located in the plane of the felt in which condition the bowed roll exerts no influence on the felt orientation, or can be rotated into the felt such that the bowed roll advances or retards the center of the felt with respect to its edges, thereby to compensate for a frown or smile condition. Thus, a smile condition such as illustrated by dashed trade line 46' on felt 30 can be removed by rotating the bowed roll 43 to retard the center of the felt with respect to its edges until the straightened condition illustrated by trade line 46 is achieved.
23-147/rnjc MsO81702511 ~2~
The felts 32, 3~ and their associated roll arrangements 33, 35 are arranged in a similar fashion to that illustrated in connection with exemplary felt section 30. Suffice it to say that both have means for adjusting the orientation of the felt, and such means preferably includes at least a seam straightener roll 33a, 35a, similar to roll 42, and a bowed roll 33b similar to bowed roll 43. However, in some cases as illustrated by lower felt 34, only a seam straightener roll 35a without the provision of a bowed roll may be adequate.
The press section arrangement of Fig. l illustrates a first nip 22 in which the paper web 21 is compressed between opposed blankets 30, 34 and subsequent nips 23, 24 where the paper web is compressed between a single felt and a press roll.
For example, in the case of nip 23, the web 20 is compressed between press roll 50 and felt 30. The web then continues its travel in contact with roll 50 whereupon it enters nip 24 where it is again compressed, but this time against felt 32. In each of the nips, the compression with the felt tends to remove additional water from the web, and as noted above, the felt then continues its travel through a drying section whereby it is again ready to remove additional water from another section of the web when it again passes through the nip.
The nips through which the web and felt or felts are passed are typically loaded by mechanical means such as linkages actuated by hydraulic or pneumatic cylinders. ~he resulting mechanical system thus has a natural frequency, and if that frequency is excited during the operation of the papermaking machine, resonance and web defects are likely to result.
23-1~7/mjc ~ ~ 2 ~ 7 One type of such defect is illustrated in exaggerated fashion in Fig. 2. That drawing schematically illustrates, on an enlarged scale and in cross-section, a portion of the fell 30 with bars 30a in the form of thickness variation ranging from a major dimension tl to a minor dimension t2. Such thickness variations, normally referred to in the trade as bars, are created by variation in pressure in the nip, the pressure variation usually resulting from resonant vibration of the elements forming the nip. It will be appreciated that only a minor thickness variation from tl to t2 in the first instance can initiate a more substantial vibration problem, because when the felt travels around its looped path and returns to the nip, if the high point of the felt again excites the nip rollers, the perturbation will increase in magnitude and ultimately produce significant thickness variations in the felt as illustrated in Fig. 2. The variations can be in the form of thickness variations as illustrated in Fig. 2, and can also take the form of hydrodynamic variations, e.g., cyclic variations in water loading along the length of the felt. In any event, the resonant frequency in the nip can introduce mechanical variations in the felt which if continually reintroduced into the nip at a speed related to the resonant frequency of the nip system can cause significant mechanical variations in the felt. Such mechanical variations will of course translate into variations in the web, such as thiclcness variations in the web, which can cause the production of an unacceptable final product.
While the bowed roll adjustment 43 and seam straightener adjustment 42 have been available in the past for altering the travel of the felt through the 23-147/mjc ~2~
nip (for example, by advancing one edge ahead of the other or the center with respect to the edges), such adjustments have served as only a temporary fix since the felt, if it continued to run at a speed related to the resonant frequency of the nip system, can bar in the new direction after an adjustment is made.
In accordance with the invention, the press section of Fig. 1 is provided with apparatus for progressively adjusting the orientation trade line (preferably between a pair of predetermined limits) so that any barring which is initially introduced into the felt by perturbations in the nip is not reintroduced to the nip on subsequent passes thereby to avoid the resonant buildup which is illustrated in Fig. 2. The progressive adjustment of trade line orientation is intended in its broad sense to include progressive adjustment of the trade line angle with respect to the press (e.gO, a seam straightener adjustment), or the trade line shape (e.g., a bowed roll adjustment). Progressive adjustment is intended to encompass an adjustment sufficiently continuous to adjust trade line orientation with sufficient rapidity over time to minimize barring buildup in the felt as the papermaking machine continues to run.
Thus, while in some cases it may be useful to run the trade line orientation adjustment means continuously, in other situations incremental adjustment may be possible so long as minor bars introduced into the felt are reoriented before substantial barring buildup can occur.
Conveniently, in the practice of the invention, standard adjustment mechanisms are used for varying the trade line orientation, but are motorized (preferably with feedback devices) so that a limited amount of relatively continuous motion can De 23~ 7/mjc MsO8170~
This invention relates to papermaking machines and more particularly to the press section of high speed papermaking machines and means for reducing vibration in the press section.
BACKGROUND OF THE INVENTION
In papermaking, it is well-known that a paper web is formed from a slurry on a web-forming wire~
and water is removed from the web as it travels through the papermaking machine until the fully dewatered and treated web is wound on a reel at the end of the machine. While this brief statement clearly oversimplifies the papermaking process, it is adequate to direct attention to the press section which is the papermaking machine section of primary interest to the instant invention. More particularly, after the web is formed and partially dewatered in the forming section, the web is passed to a press section where it is carried on dewatering felts and passed between press rolls forming one or more nips. The purpose of the felts and the nips is to remove water from the web, such as by transferring water from the web to the felts.
In conventional papermaking machines, the felts are driven over a plurality of rolls which are mounted in the machine frame to form a path for the felt in a continuous loop. In addition to the aforementioned nips, the rolls which form the loop typically include certain adjustable rolls for adjusting the felt orientation; such adjustable rolls are often configured as seam straighteners or bowed rolls. The press felt itself is in the form of a continuous loop and usually has a trade line which is formed on the felt during its manufacture in such a 23-1~17/mjc way as to relate the pattern of the weave in the felt to the visually perceptible trade line. For example, the trade line is usually painted or otherwise marked on the felt parallel to the orientation of the felt weave so that if the trade line is running square with respect to the press, the operator knows that the weave is uniformly open across the press. It will be appreciated that the felt is usually a woven material, the roll in the press section can tension one part of the felt with respect to others, and the woven material being resilient will deform to accon~odate the new adjustment. The trade line is an indicator of how the weave pattern has accommodated itself to an~ particular press section felt roller adjustment. Thus, if the trade line is bowed or otherwise in a nonlinear orientation, the press operator has information as to which parts of the felt weave are more open or more closed with respect to other parts.
In summary, when the continuous felt loop is installed in a press section, and the felt is run in its continuous loop, the trade line gives an indication of whether the weave pattern is linear across the machine and straight, whether the weave pattern is bowed, or whether one edge is running ahead of the other. The seam straightener is a roll which is journalled such that one end can be advanced or retarded with respect to the other, for the purposes of getting the edges of the felt trade line in the same orientation with respect to each othèr across the press. The bowed roll has a curved axis and can have this axis advanced into or retracted from the felt so as to adjust the center of the felt with respect to its edges thereby to accon~odate for what is called a smile or a frown in the felt.
23-1~7/mjc ~3~ ~L~
Together, the bowed roll and seam straightener are utilized to adjust the orientation of the trade line of the felt with respect to the press section.
Preferably, they adjust the trade line so that it is in a straight line and square with respect to the press, i.e., perpendicular to the machine direction of the press. As a result, the felt weave pattern will be the same orientation across the press (the holes in the weave pattern will not be compressed more in one section than in another due to the fe]t running out of square), and thus the felt will be equally effective across the papermaking machine for removing water f rom the web.
As papermaking machine speeds have increased, vibration has become more and more of a problem.
Excessive vibration tends to introduce unacceptable thickness variations in the formed paper web. One important source of such vibrations is in the nip of the press section, and can result from resonances in the press nip excited by variations in the felt originally created by nip vibrations. When the discontinuities in the felt ~such as bars as will be explained below) arrive at the nip at a frequency which will excite the mechanical system, constructive interference can result, resulting in excessive vibrations and a detrimental effect on web quality.
Thus, if the felt in passing through the nip experiences a change in pressure adequate to cause a slight thickness variation in the felt, on a subsequent pass of the felt through the same nip, that minor thickness variation can again excite the nip to cause a more pronounced vibration. Subsequent cycles can cause a resonant buildup which tends to enhance the thickness variations in the felt, causing a condition known in the trade as barring. The ~3-1~7/m~c MsO81702511 - ~2~
barred felt which continuously passes through the nip, excites the nip, and when the bars are at a predetermined interval for a given press speed and mechanical resonant frequency, the resonances can cause significant thickness variations in the felt, which in turn have an unacceptable effect on the thickness uniformity of the produced web.
It has sometimes been the practice in the past to attempt to deal with felt barring by periodically IsaY on a daily basis) slightly altering the trade line in the press (such as by adjusting the seam straightener) so that the bars created on one day go through the nip on another day out of square and thus do not continue to resonantly excite the apparatus.
However, the felt in its new orientation can create a new set of bars which over the course of the day or until the next adjustment can cause a new set of bars with the accompanying vibration and deterioration of web quality.
SUM~ARY OF THE INVENTION
In view of the foregoing, it is a general aim of the present invention to minimize vibration in the press section of a high speed papermaking machine heretofore caused by resonances carried through the press section by deformations introduced in the felt.
In accomplishing that aim, an object of the present invention is to control the press section in such a way as to minimize vibrations occasioned by resonances excited by the continuous cycling of the press section felts through the nips.
According to a more detailed aspect of the invention, it is an object to reduce resonant vibration in the press section occasioned by resonance excited by the felt, but in such a way as 23-1~7/mjc MB081702~11 ~ ~ 2 ,~
to minimize the effect on the formed web of felt trade line variations.
Other objects and advantages will become apparent from the following detailed description when taken in conjunction with the drawings, in whi~h:
BRIEF DESCRIPTION OF TH~ DRAWINGS
Figure l is a diagrammatic view in perspective illustrating the press section of a papermaking machine;
Fig. 2 is a diagram illustrating the barring phenomenon on a press felt shown in exaggerated cross section;
Fig. 3 is a diagram showing the control elements of the press section of Fig. l adapted for practice of the present invention;
Fig. 4 is a diagram similar to Fig. 3 but in plan view also illustrating the control elements of the press section of Fig. l adapted for practice of the present invention; and Figs. 5 and 6 are a partial schematic diagrams in plan view illustrating progressive adjustment of the trade line orientation for minimizing resonant vibration in the nip of a press section according to the present invention.
While the invention will be described in connection with certain preferred embodiments, there is no intent to limit it to those embodiments. On the contrary, the intent is to cover all alternatives, modifications and equivalents included within the spirit and scope of the invention as defined by the appended claims.
23-1~7/mjc MB081/0~
~2~7 DETAILED DESCRIPTION O~ THE PREFERRED EMBODIMENTS
Turning now to the drawings, Fig. 1 shows schematically and in partial perspective a press section of a papermaking machine. A partly formed and partly dewatered web 20 enters the press section at 21 and passes through several nips 22, 23, 24 where pressure is applied to remove additional water, whereupon the web exits the press section at 25 for passage to downstream equipment such as the dryer.
The illustrated press section includes three press felts 30, 32, 34, each of such felts having an associated roll arrangement 31, 33, 35 about which the associated felt is driven in a continuous loop.
Taking the press felt 30 as exemplary, it is seen that the roll arrangement 31 which defines the loop about which the felt is driven includes a nip roll (or press roll3 40, a plurality of guide rolls 41, a seam straightener roll 42, and a bowed roll 43.
Dryer means 44 are disposed adjacent the felt 30 for removing water from the felt, such as by suction, after the web has left the felt, such that the felt is dried in preparation for again contacting the web ~0 and passing through the nip 22.
The seam straightener roll 42, as will be described in greater detail below, is arranged to tension the felt 30, and also to adjust one end of the felt forward or rearward with respect to the other end, thereby to adjust the orientation of the felt trade line. The trade line for the felt 30 is illustrated at 46 and is seen to be a visible line marked or painted across the felt. In manufacture, the trade line 46 is located on the felt in a predetermined relationship (generally parallel to) the felt weave, such that when the trade line 46 is perpendicular with respect to the path of felt travel 23-1~7/mjc MsO81702511 ~2~
in the press, the felt weave is also square with respect to travel and thus the weave across the felt is open and uniform across the felt. However, when the felt is run with one end leading the other, as illustrated by the trade line 48 on felt 32, the pores of the felt are partly closed due to the skew of the weave. When the felt is run with a smile or a frown, the degree of pore opening varies across the press. In order to correct the trade line orientation from the skewed condition as illustrated at 48, to the squared condition illustrated by trade line 46, the seam straightener roll 42 for the felt in question is adjusted to either retard or advance the forward edge of the felt until the trade line assumes the position of trade line 46, i.e., perpendicular to the direction of travel.
It is also possible for the felt to be tensioned in the press section such that the center is trailing or leading with respect to one or both of the edges, a condition referred to in the trade as smile or frown. The bowed roll 43 has a curvature which can be oriented by an adjustment mechanism such that the curvature or bow can be located in the plane of the felt in which condition the bowed roll exerts no influence on the felt orientation, or can be rotated into the felt such that the bowed roll advances or retards the center of the felt with respect to its edges, thereby to compensate for a frown or smile condition. Thus, a smile condition such as illustrated by dashed trade line 46' on felt 30 can be removed by rotating the bowed roll 43 to retard the center of the felt with respect to its edges until the straightened condition illustrated by trade line 46 is achieved.
23-147/rnjc MsO81702511 ~2~
The felts 32, 3~ and their associated roll arrangements 33, 35 are arranged in a similar fashion to that illustrated in connection with exemplary felt section 30. Suffice it to say that both have means for adjusting the orientation of the felt, and such means preferably includes at least a seam straightener roll 33a, 35a, similar to roll 42, and a bowed roll 33b similar to bowed roll 43. However, in some cases as illustrated by lower felt 34, only a seam straightener roll 35a without the provision of a bowed roll may be adequate.
The press section arrangement of Fig. l illustrates a first nip 22 in which the paper web 21 is compressed between opposed blankets 30, 34 and subsequent nips 23, 24 where the paper web is compressed between a single felt and a press roll.
For example, in the case of nip 23, the web 20 is compressed between press roll 50 and felt 30. The web then continues its travel in contact with roll 50 whereupon it enters nip 24 where it is again compressed, but this time against felt 32. In each of the nips, the compression with the felt tends to remove additional water from the web, and as noted above, the felt then continues its travel through a drying section whereby it is again ready to remove additional water from another section of the web when it again passes through the nip.
The nips through which the web and felt or felts are passed are typically loaded by mechanical means such as linkages actuated by hydraulic or pneumatic cylinders. ~he resulting mechanical system thus has a natural frequency, and if that frequency is excited during the operation of the papermaking machine, resonance and web defects are likely to result.
23-1~7/mjc ~ ~ 2 ~ 7 One type of such defect is illustrated in exaggerated fashion in Fig. 2. That drawing schematically illustrates, on an enlarged scale and in cross-section, a portion of the fell 30 with bars 30a in the form of thickness variation ranging from a major dimension tl to a minor dimension t2. Such thickness variations, normally referred to in the trade as bars, are created by variation in pressure in the nip, the pressure variation usually resulting from resonant vibration of the elements forming the nip. It will be appreciated that only a minor thickness variation from tl to t2 in the first instance can initiate a more substantial vibration problem, because when the felt travels around its looped path and returns to the nip, if the high point of the felt again excites the nip rollers, the perturbation will increase in magnitude and ultimately produce significant thickness variations in the felt as illustrated in Fig. 2. The variations can be in the form of thickness variations as illustrated in Fig. 2, and can also take the form of hydrodynamic variations, e.g., cyclic variations in water loading along the length of the felt. In any event, the resonant frequency in the nip can introduce mechanical variations in the felt which if continually reintroduced into the nip at a speed related to the resonant frequency of the nip system can cause significant mechanical variations in the felt. Such mechanical variations will of course translate into variations in the web, such as thiclcness variations in the web, which can cause the production of an unacceptable final product.
While the bowed roll adjustment 43 and seam straightener adjustment 42 have been available in the past for altering the travel of the felt through the 23-147/mjc ~2~
nip (for example, by advancing one edge ahead of the other or the center with respect to the edges), such adjustments have served as only a temporary fix since the felt, if it continued to run at a speed related to the resonant frequency of the nip system, can bar in the new direction after an adjustment is made.
In accordance with the invention, the press section of Fig. 1 is provided with apparatus for progressively adjusting the orientation trade line (preferably between a pair of predetermined limits) so that any barring which is initially introduced into the felt by perturbations in the nip is not reintroduced to the nip on subsequent passes thereby to avoid the resonant buildup which is illustrated in Fig. 2. The progressive adjustment of trade line orientation is intended in its broad sense to include progressive adjustment of the trade line angle with respect to the press (e.gO, a seam straightener adjustment), or the trade line shape (e.g., a bowed roll adjustment). Progressive adjustment is intended to encompass an adjustment sufficiently continuous to adjust trade line orientation with sufficient rapidity over time to minimize barring buildup in the felt as the papermaking machine continues to run.
Thus, while in some cases it may be useful to run the trade line orientation adjustment means continuously, in other situations incremental adjustment may be possible so long as minor bars introduced into the felt are reoriented before substantial barring buildup can occur.
Conveniently, in the practice of the invention, standard adjustment mechanisms are used for varying the trade line orientation, but are motorized (preferably with feedback devices) so that a limited amount of relatively continuous motion can De 23~ 7/mjc MsO8170~
2~2~
provided within predetermined limits, to prevent resonances in the nip caused by returning perturbations imparted to the felt, but without trade line adjustments which are so extreme as to impart undesirable characteristics to the forming web.
Turning then to Fig. 3, there is shown a portion of the press section of Fig. 1 including those elements which are used in practicing the present invention. Thus, Fig. 3 shows a felt 50 which is driven in a continuous loop about a roll arrangemen~, shown only partially, the roll arrangement including a seam straightener adjustment roll 51 and a bowed roll 52. The seam straightener roll 51 has an actuator 54 for driving one end thereof, the actuator having a motorized operator 55 for controllably driving one end of the seam straightener to advance or retard near side of the felt with respect to the far side. The electrical operator 55 is driven by a control signal coupled to the operator on a control line 56. In many cases it is desirable to have a feedback signal from the operator 55, and such feedback signal is coupled by means of a line 57 to a controller 60. Thus, the controller 60 by means of signals coupled onto line 56 can drive the seam straightener to adjust the trade line in either direction, and by means of a feedback signal on line 57 can determine the degree of adjustment imparted to the felt.
In practicing the invention, direct feedback means from the felt are also provided, shown herèin as an array of sensors including a front sensor 61, a center sensor 62, and a rear sensor 63, all adapted to sense the trade line on the felt. When the trade line is a visibly perceptible mark on the felt, such as a line painted on the felt by the felt 23-1~7/mjc MB081 /0~
~2~
manufacturer, the sensors 61-63 are preferably in the form of optical sensing devices for producing a signal at the time the trade line passes under the associated sensor. Such signals are coupled by means of connections 64 to the processor 60 to provide a direct indication of the actual trade line position in the press section. The use of three or more sensors allows the system to sense not only whether the front and back edges are square or are leading one with respect to the other, but also, by means of the centrally located sensor allows the system to sense smile or frown, i.e., whether the center of the felt is leading or trailing its edges. Thus, the processor 60 has adequate information using the system of ~ig. 3 to sense not only the degree of adjustment of the seam straightener by means of feedback on line 57, but also the effect of that adjustment by actually sensing the position of the trade line orientation by means of sensors 61-63.
The controller 60 in many cases also usefully produces an output signal on a line 70 to drive an electrical operator 71 which controls an adjustment mechanism 72 to control the orientation of the bowed roll 52. Thus, the degree of smile or frown can be adjusted by means of a signal on line 70 driving operator 71. Like the operator 55, the operator 71 has a feedback mechanism associated therewith which produces an electrical signal coupled on a line 74 back to the processor 60.
Fig. 4 shows substantially the same elements as illustrated in Fig. 3, but in plan view to give a better appreciation of the position of the trade line 80 as the various adjustment mechanisms perform their functions. Thus, the seam straightener roll 51 is shown at the right of the diagram and includes 23-1~17/mjc mechanical actuating means 54 driven by electrical operator 55, which in turn is controlled by the processor 60 coupling signals to the actuator by means of connection 56. It is seen that the trade line 80 is canted with the back edge (the edge under back actuator 63 leading the front edge 61). Thus, in order to adjust the trade line 80 to be square with respect to the press, the controller 60 would couple control signals on bus 56 to drive the seam straightener 51 to advance the front edge of the roll 51 to the right as illustrated in Fig. 4, thus advancing the front edge of the felt with respect to the rear edge and bringing the trade line 80 closer to square. The adjustment is illustrated by dashed arrow 81 shown near the actuator 55 indicating the direction of movement of the seam straightener and a resulting dashed arrow 81a showing the front edge of the trade line being advanced with respect to the rear edge.
In a similar fashion, the bowed roll 52 can be rotated so that the bow (illustrated in exaggerated fashion in Fig. 4) can be directed further into or out of the plane of the felt to advance or retard the center of the felt with respect to its edges.
In practicing the invention, the controller 60 applies signals to the electrical operators to adjust the trade line 80 so that its orientation is progressively changed as the felt continues to cycle through the nip, thereby preventing the resonant buildup of perturbations in the nip which would ~e caused by the mechanical memory of ~he felt. Thus, if the felt is positioned such that the trade line 80 is in the position illustrated in Fig. 4, and the controller 60 is coupling signals to the trade line adjustment mechanism 55 to advance the trade line in 23-147/mjc 2~2~ 7 the direction indicated by the arrow 81a, bars which might originally have been introduced into the felt as indicated by dashed line 82 will thus also be advanced as indicated by arrow 82a. As a result, as the trade line advances toward square the bars are displaced away rom square so that they do not enter the nip simultaneously along their entire length, but progressively enter the nip. Thus, in accordance with the invention, the controller 60 continues to cycle the trade line (and any resulting bars) in such a way that the felt enters the nip in a slightly different orientation over time. As a result, any bars which might have begun to be introduced into the felt are ironed out on subsequent passes rather than simultaneously introducing a full-width discontinuity created in a previous cycle into the nip to create a larger perturbation as has been common in the past.
Thus, it will be appreciated that whereas in the prior art perturbations into the mechanical memory of the felt might recycle through the nip and create constructive interference and e~cessive vibration, in accordance with the invention, the possibility of such constructive interference is substantially reduced by a progressive reorientation of the trade line (and thus any bars that might have been produced)~ The reorientation of the trade line which is accomplished by the seam straightener or bowed roll is schematically illustrated in Figs. S and 6, respectively. Those figures are similar to Fig. 4, and illustrate the seam straightener roll 51 and its interaction in Fig. 5 and the bowed roll 52 and its interaction in Fig. 6.
Turning first to Fig. 5, it is seen that the trade line 80 is illustrated in solid lines in a substantially square position with respect to the ~3-1~7/mjc ~2~7 machine direction of the papermaking machine (illustrated by the large arrow). In accordance with the invention, the trade line 80 is progressively adjusted between a pair of predetermined limits 180, 181 illustrated in dashed lines. It is seen that arrows 185 associated with the seam straightener actuator 54 demonstrate that the forward end of the roll is moved first to the right to its predetermined limit (whereupon the trade line position will be like that illustrated by dashed line 181. The actuator 54 then continuously cycles between that limit and the opposite limit (that associated with trade line orientation 180) at a predetermined rate, and such progressive adjustment is coordinated with the speed and other parameters of the press to minimize resonant buildup of perturbations in the nip.
Preferably, the trade line position is sensed by means of optical sensors 61-63 (Fig. 4), although such sensing can also be accomplished indirectly by means of controller po~ition feedback signals on line 57.
Fig. 6 illustrates the use of the bowed roll in progressively altering the trade line orientation.
As in Fig. 5, the initial substantially square position of the trade line is illustrated at 80, and a pair of limits for maximum frown at 182 and maximum smile at 183. The arcuate arrows 186 associated with the bowed roll actuator 72 illustrate the rotation of the bow into and out of the plane of the felt in order to cycle the trade line orientation between the predetermined limits 182, 183. It will also be appreciated that a combination of bowed roll and seam straightener actuators can be utilized together or in sequence when desired in order to provide the 23-1~7/mjc .
~2~
progressive trade line orientation adjustment described herein.
In practicing the invention the controller 60 cycles the trade line orientation, preferably by operation of the seam straightener to adjust the trade line within predetermined limits on either side of square as determined by feedback means 61-63. A
number of considerations are important in making that continuing adjustment, one of which is that the limits are set far enough apart so as to assure that any bars are ironed out rather than reintroduced to the nip for creating possible resonances, but the limits are not set so far apart as to create undesirable defects in the web which might be occasioned by uneven dewatering resulting from a weave pattern in the felt which is distorted by too great an adjustment.
The speed of the papermaking machine is also a consideration in adjusting the rate of the trade line adjustment, it being a matter of experiment to assure that the adjustment speed for the trade line as it cycles from either side of square in order to prevent perturbations is not at a frequency which is resonant at the normal operating frequency of the papermaking machine so as to avoid introduction of other resonances. Thus, the controller speed and limits are adjusted to suit the particular type of web being formed and speed of the machine to progressively cycle the trade line, preferably through center to a pair of predetermined limits on either side of square, at a rate and for a distance adequate to prevent perturbations originally introduced into the felt from resonantly disturbing the nip to introduce unacceptable vibrations in the web.
23-147/mjc ~2~A
As shown in ~ig. 4, the bowed roll 52 is also motorized and the feedback means 60 are adapted to sense adjustment made by the bowed roll, in that the measurement is made across the web, and the bowed roll can thus also be cycled to minimize vibrations. However, in most instancesl it will be adequate to simply cycle the seam straightener rather than introduce the additional complication of cycling the bowed roll. In some instances, cycling of both will be found to be useful.
The feedback mechanisms associated with the seam straightener and bowed roll actuators can be used to set the limits for the cycling adjustment in the absence of direct feedback means 61-63 which sense the trade line position. Thus, the operator can, first of all by manual intervention, arrange the trade line so that it is perpendicular with respect to the web, then couple a signal to the controller 60 indicating the center position and allow the controller 60 operating by means of feedback signals on lines 56 or 74 to determine the predetermined limits. However, in most circumstances it will be found preferable to use the actual direct feedback means 61-63 to sense the actual position of the trade line and thus exercise more complete and accurate control over the weave pattern of the felt.
It will thus be appreciated that what has been provided is an improved press section for a papermaking machine in ~hich means are provided for preventing perturbations introduced into the press felt from resonantly e~citing the nip on subsequent passes through the nlp thereby to minimize vibrations in the press section and provide better control over web thickness and mechanical characteristics.
23-1~7/n~jc
provided within predetermined limits, to prevent resonances in the nip caused by returning perturbations imparted to the felt, but without trade line adjustments which are so extreme as to impart undesirable characteristics to the forming web.
Turning then to Fig. 3, there is shown a portion of the press section of Fig. 1 including those elements which are used in practicing the present invention. Thus, Fig. 3 shows a felt 50 which is driven in a continuous loop about a roll arrangemen~, shown only partially, the roll arrangement including a seam straightener adjustment roll 51 and a bowed roll 52. The seam straightener roll 51 has an actuator 54 for driving one end thereof, the actuator having a motorized operator 55 for controllably driving one end of the seam straightener to advance or retard near side of the felt with respect to the far side. The electrical operator 55 is driven by a control signal coupled to the operator on a control line 56. In many cases it is desirable to have a feedback signal from the operator 55, and such feedback signal is coupled by means of a line 57 to a controller 60. Thus, the controller 60 by means of signals coupled onto line 56 can drive the seam straightener to adjust the trade line in either direction, and by means of a feedback signal on line 57 can determine the degree of adjustment imparted to the felt.
In practicing the invention, direct feedback means from the felt are also provided, shown herèin as an array of sensors including a front sensor 61, a center sensor 62, and a rear sensor 63, all adapted to sense the trade line on the felt. When the trade line is a visibly perceptible mark on the felt, such as a line painted on the felt by the felt 23-1~7/mjc MB081 /0~
~2~
manufacturer, the sensors 61-63 are preferably in the form of optical sensing devices for producing a signal at the time the trade line passes under the associated sensor. Such signals are coupled by means of connections 64 to the processor 60 to provide a direct indication of the actual trade line position in the press section. The use of three or more sensors allows the system to sense not only whether the front and back edges are square or are leading one with respect to the other, but also, by means of the centrally located sensor allows the system to sense smile or frown, i.e., whether the center of the felt is leading or trailing its edges. Thus, the processor 60 has adequate information using the system of ~ig. 3 to sense not only the degree of adjustment of the seam straightener by means of feedback on line 57, but also the effect of that adjustment by actually sensing the position of the trade line orientation by means of sensors 61-63.
The controller 60 in many cases also usefully produces an output signal on a line 70 to drive an electrical operator 71 which controls an adjustment mechanism 72 to control the orientation of the bowed roll 52. Thus, the degree of smile or frown can be adjusted by means of a signal on line 70 driving operator 71. Like the operator 55, the operator 71 has a feedback mechanism associated therewith which produces an electrical signal coupled on a line 74 back to the processor 60.
Fig. 4 shows substantially the same elements as illustrated in Fig. 3, but in plan view to give a better appreciation of the position of the trade line 80 as the various adjustment mechanisms perform their functions. Thus, the seam straightener roll 51 is shown at the right of the diagram and includes 23-1~17/mjc mechanical actuating means 54 driven by electrical operator 55, which in turn is controlled by the processor 60 coupling signals to the actuator by means of connection 56. It is seen that the trade line 80 is canted with the back edge (the edge under back actuator 63 leading the front edge 61). Thus, in order to adjust the trade line 80 to be square with respect to the press, the controller 60 would couple control signals on bus 56 to drive the seam straightener 51 to advance the front edge of the roll 51 to the right as illustrated in Fig. 4, thus advancing the front edge of the felt with respect to the rear edge and bringing the trade line 80 closer to square. The adjustment is illustrated by dashed arrow 81 shown near the actuator 55 indicating the direction of movement of the seam straightener and a resulting dashed arrow 81a showing the front edge of the trade line being advanced with respect to the rear edge.
In a similar fashion, the bowed roll 52 can be rotated so that the bow (illustrated in exaggerated fashion in Fig. 4) can be directed further into or out of the plane of the felt to advance or retard the center of the felt with respect to its edges.
In practicing the invention, the controller 60 applies signals to the electrical operators to adjust the trade line 80 so that its orientation is progressively changed as the felt continues to cycle through the nip, thereby preventing the resonant buildup of perturbations in the nip which would ~e caused by the mechanical memory of ~he felt. Thus, if the felt is positioned such that the trade line 80 is in the position illustrated in Fig. 4, and the controller 60 is coupling signals to the trade line adjustment mechanism 55 to advance the trade line in 23-147/mjc 2~2~ 7 the direction indicated by the arrow 81a, bars which might originally have been introduced into the felt as indicated by dashed line 82 will thus also be advanced as indicated by arrow 82a. As a result, as the trade line advances toward square the bars are displaced away rom square so that they do not enter the nip simultaneously along their entire length, but progressively enter the nip. Thus, in accordance with the invention, the controller 60 continues to cycle the trade line (and any resulting bars) in such a way that the felt enters the nip in a slightly different orientation over time. As a result, any bars which might have begun to be introduced into the felt are ironed out on subsequent passes rather than simultaneously introducing a full-width discontinuity created in a previous cycle into the nip to create a larger perturbation as has been common in the past.
Thus, it will be appreciated that whereas in the prior art perturbations into the mechanical memory of the felt might recycle through the nip and create constructive interference and e~cessive vibration, in accordance with the invention, the possibility of such constructive interference is substantially reduced by a progressive reorientation of the trade line (and thus any bars that might have been produced)~ The reorientation of the trade line which is accomplished by the seam straightener or bowed roll is schematically illustrated in Figs. S and 6, respectively. Those figures are similar to Fig. 4, and illustrate the seam straightener roll 51 and its interaction in Fig. 5 and the bowed roll 52 and its interaction in Fig. 6.
Turning first to Fig. 5, it is seen that the trade line 80 is illustrated in solid lines in a substantially square position with respect to the ~3-1~7/mjc ~2~7 machine direction of the papermaking machine (illustrated by the large arrow). In accordance with the invention, the trade line 80 is progressively adjusted between a pair of predetermined limits 180, 181 illustrated in dashed lines. It is seen that arrows 185 associated with the seam straightener actuator 54 demonstrate that the forward end of the roll is moved first to the right to its predetermined limit (whereupon the trade line position will be like that illustrated by dashed line 181. The actuator 54 then continuously cycles between that limit and the opposite limit (that associated with trade line orientation 180) at a predetermined rate, and such progressive adjustment is coordinated with the speed and other parameters of the press to minimize resonant buildup of perturbations in the nip.
Preferably, the trade line position is sensed by means of optical sensors 61-63 (Fig. 4), although such sensing can also be accomplished indirectly by means of controller po~ition feedback signals on line 57.
Fig. 6 illustrates the use of the bowed roll in progressively altering the trade line orientation.
As in Fig. 5, the initial substantially square position of the trade line is illustrated at 80, and a pair of limits for maximum frown at 182 and maximum smile at 183. The arcuate arrows 186 associated with the bowed roll actuator 72 illustrate the rotation of the bow into and out of the plane of the felt in order to cycle the trade line orientation between the predetermined limits 182, 183. It will also be appreciated that a combination of bowed roll and seam straightener actuators can be utilized together or in sequence when desired in order to provide the 23-1~7/mjc .
~2~
progressive trade line orientation adjustment described herein.
In practicing the invention the controller 60 cycles the trade line orientation, preferably by operation of the seam straightener to adjust the trade line within predetermined limits on either side of square as determined by feedback means 61-63. A
number of considerations are important in making that continuing adjustment, one of which is that the limits are set far enough apart so as to assure that any bars are ironed out rather than reintroduced to the nip for creating possible resonances, but the limits are not set so far apart as to create undesirable defects in the web which might be occasioned by uneven dewatering resulting from a weave pattern in the felt which is distorted by too great an adjustment.
The speed of the papermaking machine is also a consideration in adjusting the rate of the trade line adjustment, it being a matter of experiment to assure that the adjustment speed for the trade line as it cycles from either side of square in order to prevent perturbations is not at a frequency which is resonant at the normal operating frequency of the papermaking machine so as to avoid introduction of other resonances. Thus, the controller speed and limits are adjusted to suit the particular type of web being formed and speed of the machine to progressively cycle the trade line, preferably through center to a pair of predetermined limits on either side of square, at a rate and for a distance adequate to prevent perturbations originally introduced into the felt from resonantly disturbing the nip to introduce unacceptable vibrations in the web.
23-147/mjc ~2~A
As shown in ~ig. 4, the bowed roll 52 is also motorized and the feedback means 60 are adapted to sense adjustment made by the bowed roll, in that the measurement is made across the web, and the bowed roll can thus also be cycled to minimize vibrations. However, in most instancesl it will be adequate to simply cycle the seam straightener rather than introduce the additional complication of cycling the bowed roll. In some instances, cycling of both will be found to be useful.
The feedback mechanisms associated with the seam straightener and bowed roll actuators can be used to set the limits for the cycling adjustment in the absence of direct feedback means 61-63 which sense the trade line position. Thus, the operator can, first of all by manual intervention, arrange the trade line so that it is perpendicular with respect to the web, then couple a signal to the controller 60 indicating the center position and allow the controller 60 operating by means of feedback signals on lines 56 or 74 to determine the predetermined limits. However, in most circumstances it will be found preferable to use the actual direct feedback means 61-63 to sense the actual position of the trade line and thus exercise more complete and accurate control over the weave pattern of the felt.
It will thus be appreciated that what has been provided is an improved press section for a papermaking machine in ~hich means are provided for preventing perturbations introduced into the press felt from resonantly e~citing the nip on subsequent passes through the nlp thereby to minimize vibrations in the press section and provide better control over web thickness and mechanical characteristics.
23-1~7/n~jc
Claims (7)
OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS :
1. In a papermaking machine press section, the press section having at least one dewatering felt, the combination comprising:
a first plurality of rolls arranged to define a continuous path around which the felt is driven, a press felt arranged in a continuous loop around the rolls, the felt having a trade line disposed on the felt in a predetermined orientation, the plurality of rolls including a press roll for compressing the felt and a paper web carried thereby in a nip to dewater said web, an adjustable roll mounted for adjusting the orientation of the trade line as the felt is driven in its continuous loop around said rolls, drive means for driving the adjustable roll to alter the trade line orientation as the felt is driven around said continuous path, control means having an output coupled to the drive means for progressive varying the trade line orientation upon successive passes of the felt through the nip at a rate sufficient to minimize barring of the felt and the resulting thickness variations in the web, sensor means for sensing the orientation of the trade line, the control means being responsive to the sensor means for controlling the rate and limits of progressive variation of the trade line orientation;
the adjustable roll being a seam straightener having one end adjustable with respect to the other for varying the orientation of the trade line.
a first plurality of rolls arranged to define a continuous path around which the felt is driven, a press felt arranged in a continuous loop around the rolls, the felt having a trade line disposed on the felt in a predetermined orientation, the plurality of rolls including a press roll for compressing the felt and a paper web carried thereby in a nip to dewater said web, an adjustable roll mounted for adjusting the orientation of the trade line as the felt is driven in its continuous loop around said rolls, drive means for driving the adjustable roll to alter the trade line orientation as the felt is driven around said continuous path, control means having an output coupled to the drive means for progressive varying the trade line orientation upon successive passes of the felt through the nip at a rate sufficient to minimize barring of the felt and the resulting thickness variations in the web, sensor means for sensing the orientation of the trade line, the control means being responsive to the sensor means for controlling the rate and limits of progressive variation of the trade line orientation;
the adjustable roll being a seam straightener having one end adjustable with respect to the other for varying the orientation of the trade line.
2. In a papermaking machine press section, the press section having at least one dewatering felt, the combination comprising:
a first plurality of rolls arranged to define a continuous path around which the felt is driven, a press felt arranged in a continuous loop around the rolls, the felt having a trade line disposed on the felt in a predetermined orientation, the plurality of rolls including a press roll for compressing the felt and a paper web carried thereby in a nip to dewater said web, an adjustable roll mounted for adjusting the orientation of the trade line as the felt is driven in its continuous loop around said rolls, drive means for driving the adjustable roll to alter the trade line orientation as the felt is driven around said continuous path, sensor means for sensing the orientation of the trade line, and control means having an input responsive to the sensor means and an output for operating the drive means, the control means including means for progressively varying the trade line orientation in the nip between predetermined limits, thereby to minimize barring of the felt.
a first plurality of rolls arranged to define a continuous path around which the felt is driven, a press felt arranged in a continuous loop around the rolls, the felt having a trade line disposed on the felt in a predetermined orientation, the plurality of rolls including a press roll for compressing the felt and a paper web carried thereby in a nip to dewater said web, an adjustable roll mounted for adjusting the orientation of the trade line as the felt is driven in its continuous loop around said rolls, drive means for driving the adjustable roll to alter the trade line orientation as the felt is driven around said continuous path, sensor means for sensing the orientation of the trade line, and control means having an input responsive to the sensor means and an output for operating the drive means, the control means including means for progressively varying the trade line orientation in the nip between predetermined limits, thereby to minimize barring of the felt.
3. The combination as set forth in claim 2, wherein the adjustable roll is a seam straightener having one end adjustable with respect to the other, thereby to vary the trade line orientation of the felt.
4. The combination as set forth in claim 2, wherein the adjustable roll is a bowed roll adjustable to vary the orientation of the center of the felt with respect to the felt edges thereby to vary the trade line orientation.
S. The combination as set forth in claim 2, wherein the sensor means comprise at least three optical sensors for sensing the trade line variation at the felt edges and center thereby to sense trade line orientation.
6. The combination as set forth in claim 5, wherein the control means is responsive to the sensor means for adjusting the position of the adjustable roller between said predetermined limits as detected by said sensor means.
7. The combination as set forth in claim 2, wherein the drive means includes feedback means for producing a signal indicating the amount of adjustment accomplished by said drive means, the control means including means responsive to the feedback means for establishing said predetermined limits.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| US43406489A | 1989-11-07 | 1989-11-07 | |
| US07/434,064 | 1989-11-07 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2025447A1 CA2025447A1 (en) | 1991-05-08 |
| CA2025447C true CA2025447C (en) | 1995-01-17 |
Family
ID=23722671
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002025447A Expired - Lifetime CA2025447C (en) | 1989-11-07 | 1990-09-14 | Method and apparatus for reducing vibration in the press section of a papermaking machine |
Country Status (2)
| Country | Link |
|---|---|
| JP (1) | JPH03152290A (en) |
| CA (1) | CA2025447C (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2012130692A1 (en) * | 2011-03-25 | 2012-10-04 | Voith Patent Gmbh | Method for operating a press fabric in a fibrous-web manufacturing machine |
| CN103046419A (en) * | 2011-10-14 | 2013-04-17 | 美卓造纸机械公司 | Method and arrangement for fiber web machine, and software product |
Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FI100412B (en) * | 1991-05-21 | 1997-11-28 | Valmet Paper Machinery Inc | A system in the press section of a paper machine for monitoring and controlling the flow of press felts |
| AT508331B1 (en) * | 2009-05-19 | 2011-05-15 | Andritz Ag Maschf | METHOD AND DEVICE FOR TREATING A FIBROUS CAR TRACK IN A LANGNIP PRESS UNIT |
Family Cites Families (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS5146847B2 (en) * | 1972-12-29 | 1976-12-11 | ||
| JPS5146165B2 (en) * | 1973-11-13 | 1976-12-07 | ||
| FI790105A7 (en) * | 1979-01-12 | 1980-07-13 | Valmet Oy | FOERFARANDE OCH ANORDNING FOER BEHANDLING AV FIBERBANA |
-
1990
- 1990-09-14 CA CA002025447A patent/CA2025447C/en not_active Expired - Lifetime
- 1990-10-13 JP JP27512790A patent/JPH03152290A/en active Pending
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2012130692A1 (en) * | 2011-03-25 | 2012-10-04 | Voith Patent Gmbh | Method for operating a press fabric in a fibrous-web manufacturing machine |
| CN103046419A (en) * | 2011-10-14 | 2013-04-17 | 美卓造纸机械公司 | Method and arrangement for fiber web machine, and software product |
| CN103046419B (en) * | 2011-10-14 | 2016-06-29 | 维美德技术有限公司 | Method and apparatus for fiber web machine |
Also Published As
| Publication number | Publication date |
|---|---|
| JPH03152290A (en) | 1991-06-28 |
| CA2025447A1 (en) | 1991-05-08 |
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| EEER | Examination request | ||
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Effective date: 20121202 |