CA1232162A - Press section for a paper machine - Google Patents
Press section for a paper machineInfo
- Publication number
- CA1232162A CA1232162A CA000453481A CA453481A CA1232162A CA 1232162 A CA1232162 A CA 1232162A CA 000453481 A CA000453481 A CA 000453481A CA 453481 A CA453481 A CA 453481A CA 1232162 A CA1232162 A CA 1232162A
- Authority
- CA
- Canada
- Prior art keywords
- nip
- web
- roll
- press
- fabric
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
- D21F3/00—Press section of machines for making continuous webs of paper
- D21F3/02—Wet presses
- D21F3/04—Arrangements thereof
Abstract
ABSTRACT OF THE DISCLOSURE
An improvement in a press section for a paper machine which includes at least four successive nips between which the web runs as a closed draw supported on a fabric or roll face. A first fabric functions as a pick-up felt and to carry the web into the first dewatering press nip formed between a first pair of press rolls. A second fabric carries the web from the first nip into the second nip whereupon the web is detached from the second fabric to follow along with an upper roll of the second nip into the third nip formed between the upper roll of the second nip and a smooth-faced roll. A fourth nip is formed between the smooth-faced roll and a dewatering press roll.
Dewatering takes place through both faces of the web in the first nip, through only one face of the web in the second nip and in the fourth nip through the other face of the web in a direction opposite from the dewatering direction in the second nip. The third nip is a substantially non-dewatering smoothing and transfer nip. According to the invention, a belt felt runs over a sector of the upper roll of the second nip between and through the second and third nips. The belt felt is substantially water non-receiving and has a smooth-faced outer surface. The web adheres to the belt felt after detachment from the second fabric and is carried into the third nip while supported on the belt felt. After passing through the third nip, the web is detached from the belt felt at least in part due to its surface properties and adheres to the smooth-faced press roll on which it is carried into the next dewatering nip.
An improvement in a press section for a paper machine which includes at least four successive nips between which the web runs as a closed draw supported on a fabric or roll face. A first fabric functions as a pick-up felt and to carry the web into the first dewatering press nip formed between a first pair of press rolls. A second fabric carries the web from the first nip into the second nip whereupon the web is detached from the second fabric to follow along with an upper roll of the second nip into the third nip formed between the upper roll of the second nip and a smooth-faced roll. A fourth nip is formed between the smooth-faced roll and a dewatering press roll.
Dewatering takes place through both faces of the web in the first nip, through only one face of the web in the second nip and in the fourth nip through the other face of the web in a direction opposite from the dewatering direction in the second nip. The third nip is a substantially non-dewatering smoothing and transfer nip. According to the invention, a belt felt runs over a sector of the upper roll of the second nip between and through the second and third nips. The belt felt is substantially water non-receiving and has a smooth-faced outer surface. The web adheres to the belt felt after detachment from the second fabric and is carried into the third nip while supported on the belt felt. After passing through the third nip, the web is detached from the belt felt at least in part due to its surface properties and adheres to the smooth-faced press roll on which it is carried into the next dewatering nip.
Description
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PRESS SECTION FOR A PAPER MACHINE
This invention relates generally to paper making machines and, more particularly, to press sections for paper machines.
The present invention is specifically directed to a paper machine press section which comprises at least four successive nips between which the web from which water is drained runs as a closed draw, i.e., without any open draws, supported on a fabric or roll face, the nips being constructed and arranged so that detouring of the web takes place substantially symmetrically and to a substantially equal extent through both faces of the web. The press section includes a first fabric which functions as a pick-up felt onto the lower face of which the web is transferred from the forming wire to be carried into a first detouring press nip formed between a first pair of press rolls in which a second fabric comprises a lower felt. The web is carried from the first nip by the second fabric into the second nip formed between a second pair of rolls, the web being detached from the second fabric after the second nip to follow along with the upper roll of the second nip into the third nip formed between the upper roll of the second nip and a smooth-faced roll. The fourth nip of the press section, which is a detouring nip and is provided with a press felt of its own, is formed between the smooth-faced roll and another press roll.
The nips are arranged in a manner such that detouring of the web takes place in the first nip through both faces of the web, and in the second nip substantially through only one face of the web, namely that face contacting the second fabric, and in the fourth nip in the opposite direction relative to the detouring direction in the second nip. The third nip is a substantially non-dewatering smoothing and transfer nip.
In paper machines which run at high speeds or which are used for the manufacture of low-strength paper qualities, i.e., fine-paper machines, so-called I" ,
PRESS SECTION FOR A PAPER MACHINE
This invention relates generally to paper making machines and, more particularly, to press sections for paper machines.
The present invention is specifically directed to a paper machine press section which comprises at least four successive nips between which the web from which water is drained runs as a closed draw, i.e., without any open draws, supported on a fabric or roll face, the nips being constructed and arranged so that detouring of the web takes place substantially symmetrically and to a substantially equal extent through both faces of the web. The press section includes a first fabric which functions as a pick-up felt onto the lower face of which the web is transferred from the forming wire to be carried into a first detouring press nip formed between a first pair of press rolls in which a second fabric comprises a lower felt. The web is carried from the first nip by the second fabric into the second nip formed between a second pair of rolls, the web being detached from the second fabric after the second nip to follow along with the upper roll of the second nip into the third nip formed between the upper roll of the second nip and a smooth-faced roll. The fourth nip of the press section, which is a detouring nip and is provided with a press felt of its own, is formed between the smooth-faced roll and another press roll.
The nips are arranged in a manner such that detouring of the web takes place in the first nip through both faces of the web, and in the second nip substantially through only one face of the web, namely that face contacting the second fabric, and in the fourth nip in the opposite direction relative to the detouring direction in the second nip. The third nip is a substantially non-dewatering smoothing and transfer nip.
In paper machines which run at high speeds or which are used for the manufacture of low-strength paper qualities, i.e., fine-paper machines, so-called I" ,
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closed draw systems are necessary so that the web is always supported by means of a felt as it passes from the wire section to the press section. These systems operate in a manner such that the transfer felt of the press section is passed into contact with the web on the wire. The transfer felt may be pressed against the web on the wire by means of a rotary roll so that the web adheres to the felt and is detached from the wire whereupon the web carrying felt carries the web into the first press nip of the press section.
us is well known, the pick-up arrangement and press section of a paper machine utilizes several press felts which function both as means for supporting the web and, additionally, as means which contribute to the detouring of the web in the various press nips.
Ordinarily, a single felt is provided at each web treatment point although in certain cases a single felt may contribute to the treatment of the web at two or even more points.
The invention constitutes an improvement in the "Simpers" press section available from the company Valet Ox of Finland, the applicant herein, and has resulted from several years of experience in the use of the "Simpers" press section.
Reference is made to our published Finnish Patent Application No. 50,651, which corresponds to US.
Patent 4,285,766, in connection with the details of the construction of the "Simpers" press section. The "Simpers" press section is a compact, fully closed press section in which the paper web coming from the wire is passed through a first nip formed between two hollow-faced and/or suction rolls and between two felts such that the detouring of the paper web takes place through both of the web faces. The press section further includes a smooth-faced roll provided with at least one doctor and which forms the second nip with one of the rolls of the first nip. Detouring of the web takes place in the second nip through the face of the web that is in contact with the second roll in the Do MURK
closed draw systems are necessary so that the web is always supported by means of a felt as it passes from the wire section to the press section. These systems operate in a manner such that the transfer felt of the press section is passed into contact with the web on the wire. The transfer felt may be pressed against the web on the wire by means of a rotary roll so that the web adheres to the felt and is detached from the wire whereupon the web carrying felt carries the web into the first press nip of the press section.
us is well known, the pick-up arrangement and press section of a paper machine utilizes several press felts which function both as means for supporting the web and, additionally, as means which contribute to the detouring of the web in the various press nips.
Ordinarily, a single felt is provided at each web treatment point although in certain cases a single felt may contribute to the treatment of the web at two or even more points.
The invention constitutes an improvement in the "Simpers" press section available from the company Valet Ox of Finland, the applicant herein, and has resulted from several years of experience in the use of the "Simpers" press section.
Reference is made to our published Finnish Patent Application No. 50,651, which corresponds to US.
Patent 4,285,766, in connection with the details of the construction of the "Simpers" press section. The "Simpers" press section is a compact, fully closed press section in which the paper web coming from the wire is passed through a first nip formed between two hollow-faced and/or suction rolls and between two felts such that the detouring of the paper web takes place through both of the web faces. The press section further includes a smooth-faced roll provided with at least one doctor and which forms the second nip with one of the rolls of the first nip. Detouring of the web takes place in the second nip through the face of the web that is in contact with the second roll in the Do MURK
3 ~:32~%
first nip. In this prior art press section there is at least one additional nip after the second nip which is formed between the smooth-faced roll, which constitutes a central roll whose diameter is larger than the diameters of the other press rolls in the press section, and a hollow-faced roll. A felt runs through this additional nip which is situated at a point on the central roll which is substantially diametrically opposite from the point of the central roll at which the second nip is formed.
lo The conventional press section described above has a possible drawback in that it does not provide a fully symmetric detrain of the web in so far as the distribution of fines and filler agents under all circumstances and, in particular, in the case of fine paper grades.
A drawback of conventional press sections is that it is not possible in all cases to obtain a sufficiently smooth face on both sides of the web. The provision of smooth faces on both sides of the web becomes quite important in the case of fine paper grades.
With respect to the prior art which to applicant's knowledge is most closely related to the present invention, reference is made to published European Patent Application No. 81 630083.4 (Publication No.
0055206) of Bullet Corporation. A press section is disclosed therein similar to the press section to which the present invention is directed In this press section the upper roll of the second nip is a press roll having a porous elastomers coating. This press roll, which forms two nips in conjunction with other rolls, is subjected to large loads and a siyniflcant drawback of the press section is that it has been found difficult to obtain a sufficiently durable elastic coating for this press roll. For this reason it has been necessary to replace this press roll on a frequent basis. Such roll replacement is a cumbersome operation which results in relatively long down times for the 321~
paper machine. At the same time the acquisition and storage of several reserve rolls is expensive and requires significant storage space. Moreover, difficulties have also been encountered in achieving a balance between the porosity of the roll on the one hand and a sufficient smoothness of the roll face on the other hand, particularly for the manufacture of fine paper grades.
In accordance with the present invention there is provided an improvement in a press section for a paper machine including at least four successive nips between which the web from which water is drained runs as a closed draw supported on at least one of a fabric and roll face, without open draw, and in which press section the web is detoured substantially symmetrically through both faces of the web, the press section including a first fabric which functions as a pick-up felt and onto a lower face of which the web adheres, a first detouring press nip formed between a first pair of press rolls into which the web is carried by the first fabric which comprises an upper fabric in the first detouring press nip, a second fabric comprising a lower felt in the first detouring press nip, a second nip formed between a second pair of upper and lower rolls and into which the web is carried by the second fabric, a third substantially non-dewatering smoothing and transfer nip formed between the upper roll of the second nip and a smooth-faced roll, the web being detached from the second fabric after passing throuyh the second nip to follow along with the upper roll of the second nip into the third nip, a fourth detouring nip formed between the smooth-faced roll and a detouring press roll, a press felt passing through the fourth detouring nip, and wherein the first, second, third and fourth nips are arranged such that in the first nip detouring takes place through both races of the web, in the second nip detouring takes place in a first direction through only the one face of the web which contacts the second fabric which carries the web into the second nip, and in the fourth nip detouring wakes place in a second direction opposite from the first direction.
The improvement of the invention comprises a belt felt running over a sector ox the face of the upper roll of the second nip between and through the second and third nips, the belt felt being substantially water non-receiving and having a smooth-faced outer surface having surface properties such that the web is detached from the second fabric after passing through the second nip and adheres to the belt felt and is supported thereon, the belt felt transferring the web into the third substantially non-dewatering smoothing and transfer nip, whereupon the web becomes detached from the belt felt at least in part due to the surface properties thereof and adheres to the smooth-faced press roll of the third nip on the face of which the Deb is carried into the fourth press nip.
By constructing a paper making machine in this way, there is achieved full symmetric detouring of the paper web with respect to the distribution of fines and filler agents under all circumstances, and, in particular, in the manufacture of fine paper grades.
When a smooth-faced belt felt is run over a sector of the upper roll of the second nip in accordance with the invention, that roll also constituting a lower roll in the third nip, the smoothness of the outer face of the belt felt can be optimally selected in view of the desired smoothness of the face of the web to be manufactured since the belt felt need not be a water-receiving element. Moreover, replacement of the belt felt can be carried out considerably more rapidly than, for example, the replacement of the roll provided with an elastic and porous coating and which operates in a corresponding position in accordance with the teachings of the aforementioned European Patent Application Publication No. 0055206. It is also more economical to maintain a reserve stock of belt felts as compared to the costs required for maintaining a stock of corresponding elastomers covered rolls. Further, transfer of the web onto the smooth-faced roll forming the third press nip together with the upper roll of the second press nip becomes more reliable when the web is conducted by means of the belt felt in accordance with the present invention.
A more complete appreciation of the present invention and many of the attendant advantages thereof will be readily understood by reference to the following detailed description when considered in connection with the accompanying drawing in which the sole figure is a schematic side elevation view of a press section constructed in accordance with the present invention, illustrating a portion of the frame lo construction as well as portion of the wire and drying sections of the paper machine.
Referring now to the drawing; a web, such as a fine paper web, which has been drained on a forming wire 10 is transferred onto a first felt 20 of the press section in the region of a suction zone aye of a pick-up roll 24 at the detachment point P on the run of the forming wire 10 between rolls 11 and 12. The web W
adheres to the bottom face of the first felt 20 on the suction zone aye of the pick-up roll 24 and is transferred on the bottom face of the felt 20 to the press section.
The first detouring press nip No in the press section is formed between a first pair of press rolls including a lower suction roll 32 having a suction zone aye and an upper press roll 22 provided with a hollow face 23. The first felt 20, guided by guide rolls 21, comprises an upper press fabric in the first nip No. A
lower felt 30 guided by guide rolls 31 acts as the lower fabric in the first press nip No. The first nip No thus constitutes a double felled press nip and the web is detoured therein in a highly efficient manner substantially symmetrically through both faces of the web W, i.e., both upwardly and downwardly. The first 7 1 23~
felt 20 is reconditioned by conventional felt reconditioning means 25. The pick-up roll 24 is fastened to a projecting portion 26 of the frame 100 of the press section by means of pivotal side supports 27.
The second detouring press nip No in the press section is formed between a second pair of upper and lower rolls, namely a lower roll 33 having a hollow face 34 and an upper roll 42. The second felt 30 carries the web into the second nip No and acts as a lower fabric therein. As seen in the figure, the first and second nips No and No are substantially horizontal nips and the second fabric 30 and the web supported thereby has a substantially horizontal run between the first and second nips. After passing through the second nip No, the web W adheres to the outer surface of the belt felt 40 and changes its direction to follow the belt felt over a sector of the face of the upper roll 42 of the second nip No. The magnitude of the central angle defined by the sector of the upper roll 42 over which the belt felt and web carried thereby change direction is in the range of between about 90 to 180, and preferably is in the range of between about 120 to 150.
In accordance with the present invention, the belt felt 40 which is arranged to run around the upper roll 42 of the second nip No guided by guide rolls 41 has a smooth-faced outer surface. Moreover, it is an essential characteristic of the belt felt 40 that it is substantially water non-receiving and that its surface is sufficiently smooth that the web W after passing through the second nip No adheres to and follows along with the belt felt 40, i.e., is detached from the second, water-receiving felt 30 which has a coarser surface than the belt felt. In addition to these functions, the belt felt 40 also functions to smooth one side of the web, which may advantageously constitute a fine-paper web W. The opposite side of the web W is smoothed against the smooth-face 44 of the roll 43 which may advantageously comprise a rock roll.
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The rock roll 43 together with the upper roll 42 of the second press nip No forms the third nip No in the press section, the third nip being mainly a transfer and smoothing nip for the web.
Importantly, the use of a belt felt I having the properties and characteristics described above in accordance with the invention eliminates the criticality of the surface properties of the press roll I Thus, -the various disadvantages inherent in, for example, the press section disclosed in the European Patent Application Publication No. 0055206 discussed above are overcome.
A fourth detouring press nip No is formed between the smooth-faced rock roll 43 and a press roll 52 having a hollow face 53. A conventional press felt 50 runs through the fourth press nip No guided by guide rolls 51. The felt 50 is reconditioned by conventional felt reconditioning means OWE
It is apparent from the foregoing that in the first nip No, detouring of the web occurs substantially symmetrically through both faces of the web. In-the second nip No, detouring takes place substantially entirely in a first direction towards the second felt 30 through only that face of the web which contacts the second felt since the belt felt 40 is substantially water non receiving. As noted above, the third nip No functions as a smoothing and transfer nip since there are no water-receiving fabrics which pass there through. In the fourth nip No, detouring takes place in a second direction towards the press felt 50, i.e., in a direction opposite from the first direction of detouring in the second nip No. In this manner, an efficient and substantially symmetrical detouring is ensured in addition to a symmetrical distribution of fines and filler agents within the web. This is important especially in the case of fine paper grades for the production of which the press section of the present invention is mainly intended The belt felt 40 may, for example, be constructed of mesh-like reinforcement fabric which provides good resistance to tension. The fabric is preferably impregnated with plastic, rubber or a similar material.
By appropriate selection of the properties of the face of the belt felt 40 that contacts the web W, it is possible to affect the properties of one face of the web and in particular its smoothness in a predictable manner as will be understood by those skilled in the art. Although the belt felt 40 may be to at least some lo extent water-receiving and even slightly air permeable, the permeability of the belt felt I has no essential significance. It will be understood that it is the properties of the surface of the belt felt 40 which contacts the web W and, in particular, the smoothness of this surface and the adhesion properties of the surface relative to the web which are important. These properties must be such as to reliably ensure that the web will follow the belt felt 40 after the second nip No, i.e., will become detached from the press felt 30.
After the last nip No, the web is detached from the smooth face 44 of the rock roll 43 by means of a guide roll 560 The face 44 of rock roll 43 is kept clean by means of a doctor 45.
After the press section, the web W is passed to a conventional drying section which includes a lead-in cylinder 62, a drying cylinder 63 of an upper line of cylinders, and a drying cylinder 64 of a lower line of drying cylinders. The web W is transferred onto a support fabric 60 as it travels over cylinder 62, the fabric 60 being guided by guide roll 61.
Obviously, numerous modifications and variations of the present invention are possible in the light of the above teachings It is therefore to be understood that within the scope of the claims appended hereto the invention may be practiced otherwise than as specifically disclosed herein.
first nip. In this prior art press section there is at least one additional nip after the second nip which is formed between the smooth-faced roll, which constitutes a central roll whose diameter is larger than the diameters of the other press rolls in the press section, and a hollow-faced roll. A felt runs through this additional nip which is situated at a point on the central roll which is substantially diametrically opposite from the point of the central roll at which the second nip is formed.
lo The conventional press section described above has a possible drawback in that it does not provide a fully symmetric detrain of the web in so far as the distribution of fines and filler agents under all circumstances and, in particular, in the case of fine paper grades.
A drawback of conventional press sections is that it is not possible in all cases to obtain a sufficiently smooth face on both sides of the web. The provision of smooth faces on both sides of the web becomes quite important in the case of fine paper grades.
With respect to the prior art which to applicant's knowledge is most closely related to the present invention, reference is made to published European Patent Application No. 81 630083.4 (Publication No.
0055206) of Bullet Corporation. A press section is disclosed therein similar to the press section to which the present invention is directed In this press section the upper roll of the second nip is a press roll having a porous elastomers coating. This press roll, which forms two nips in conjunction with other rolls, is subjected to large loads and a siyniflcant drawback of the press section is that it has been found difficult to obtain a sufficiently durable elastic coating for this press roll. For this reason it has been necessary to replace this press roll on a frequent basis. Such roll replacement is a cumbersome operation which results in relatively long down times for the 321~
paper machine. At the same time the acquisition and storage of several reserve rolls is expensive and requires significant storage space. Moreover, difficulties have also been encountered in achieving a balance between the porosity of the roll on the one hand and a sufficient smoothness of the roll face on the other hand, particularly for the manufacture of fine paper grades.
In accordance with the present invention there is provided an improvement in a press section for a paper machine including at least four successive nips between which the web from which water is drained runs as a closed draw supported on at least one of a fabric and roll face, without open draw, and in which press section the web is detoured substantially symmetrically through both faces of the web, the press section including a first fabric which functions as a pick-up felt and onto a lower face of which the web adheres, a first detouring press nip formed between a first pair of press rolls into which the web is carried by the first fabric which comprises an upper fabric in the first detouring press nip, a second fabric comprising a lower felt in the first detouring press nip, a second nip formed between a second pair of upper and lower rolls and into which the web is carried by the second fabric, a third substantially non-dewatering smoothing and transfer nip formed between the upper roll of the second nip and a smooth-faced roll, the web being detached from the second fabric after passing throuyh the second nip to follow along with the upper roll of the second nip into the third nip, a fourth detouring nip formed between the smooth-faced roll and a detouring press roll, a press felt passing through the fourth detouring nip, and wherein the first, second, third and fourth nips are arranged such that in the first nip detouring takes place through both races of the web, in the second nip detouring takes place in a first direction through only the one face of the web which contacts the second fabric which carries the web into the second nip, and in the fourth nip detouring wakes place in a second direction opposite from the first direction.
The improvement of the invention comprises a belt felt running over a sector ox the face of the upper roll of the second nip between and through the second and third nips, the belt felt being substantially water non-receiving and having a smooth-faced outer surface having surface properties such that the web is detached from the second fabric after passing through the second nip and adheres to the belt felt and is supported thereon, the belt felt transferring the web into the third substantially non-dewatering smoothing and transfer nip, whereupon the web becomes detached from the belt felt at least in part due to the surface properties thereof and adheres to the smooth-faced press roll of the third nip on the face of which the Deb is carried into the fourth press nip.
By constructing a paper making machine in this way, there is achieved full symmetric detouring of the paper web with respect to the distribution of fines and filler agents under all circumstances, and, in particular, in the manufacture of fine paper grades.
When a smooth-faced belt felt is run over a sector of the upper roll of the second nip in accordance with the invention, that roll also constituting a lower roll in the third nip, the smoothness of the outer face of the belt felt can be optimally selected in view of the desired smoothness of the face of the web to be manufactured since the belt felt need not be a water-receiving element. Moreover, replacement of the belt felt can be carried out considerably more rapidly than, for example, the replacement of the roll provided with an elastic and porous coating and which operates in a corresponding position in accordance with the teachings of the aforementioned European Patent Application Publication No. 0055206. It is also more economical to maintain a reserve stock of belt felts as compared to the costs required for maintaining a stock of corresponding elastomers covered rolls. Further, transfer of the web onto the smooth-faced roll forming the third press nip together with the upper roll of the second press nip becomes more reliable when the web is conducted by means of the belt felt in accordance with the present invention.
A more complete appreciation of the present invention and many of the attendant advantages thereof will be readily understood by reference to the following detailed description when considered in connection with the accompanying drawing in which the sole figure is a schematic side elevation view of a press section constructed in accordance with the present invention, illustrating a portion of the frame lo construction as well as portion of the wire and drying sections of the paper machine.
Referring now to the drawing; a web, such as a fine paper web, which has been drained on a forming wire 10 is transferred onto a first felt 20 of the press section in the region of a suction zone aye of a pick-up roll 24 at the detachment point P on the run of the forming wire 10 between rolls 11 and 12. The web W
adheres to the bottom face of the first felt 20 on the suction zone aye of the pick-up roll 24 and is transferred on the bottom face of the felt 20 to the press section.
The first detouring press nip No in the press section is formed between a first pair of press rolls including a lower suction roll 32 having a suction zone aye and an upper press roll 22 provided with a hollow face 23. The first felt 20, guided by guide rolls 21, comprises an upper press fabric in the first nip No. A
lower felt 30 guided by guide rolls 31 acts as the lower fabric in the first press nip No. The first nip No thus constitutes a double felled press nip and the web is detoured therein in a highly efficient manner substantially symmetrically through both faces of the web W, i.e., both upwardly and downwardly. The first 7 1 23~
felt 20 is reconditioned by conventional felt reconditioning means 25. The pick-up roll 24 is fastened to a projecting portion 26 of the frame 100 of the press section by means of pivotal side supports 27.
The second detouring press nip No in the press section is formed between a second pair of upper and lower rolls, namely a lower roll 33 having a hollow face 34 and an upper roll 42. The second felt 30 carries the web into the second nip No and acts as a lower fabric therein. As seen in the figure, the first and second nips No and No are substantially horizontal nips and the second fabric 30 and the web supported thereby has a substantially horizontal run between the first and second nips. After passing through the second nip No, the web W adheres to the outer surface of the belt felt 40 and changes its direction to follow the belt felt over a sector of the face of the upper roll 42 of the second nip No. The magnitude of the central angle defined by the sector of the upper roll 42 over which the belt felt and web carried thereby change direction is in the range of between about 90 to 180, and preferably is in the range of between about 120 to 150.
In accordance with the present invention, the belt felt 40 which is arranged to run around the upper roll 42 of the second nip No guided by guide rolls 41 has a smooth-faced outer surface. Moreover, it is an essential characteristic of the belt felt 40 that it is substantially water non-receiving and that its surface is sufficiently smooth that the web W after passing through the second nip No adheres to and follows along with the belt felt 40, i.e., is detached from the second, water-receiving felt 30 which has a coarser surface than the belt felt. In addition to these functions, the belt felt 40 also functions to smooth one side of the web, which may advantageously constitute a fine-paper web W. The opposite side of the web W is smoothed against the smooth-face 44 of the roll 43 which may advantageously comprise a rock roll.
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The rock roll 43 together with the upper roll 42 of the second press nip No forms the third nip No in the press section, the third nip being mainly a transfer and smoothing nip for the web.
Importantly, the use of a belt felt I having the properties and characteristics described above in accordance with the invention eliminates the criticality of the surface properties of the press roll I Thus, -the various disadvantages inherent in, for example, the press section disclosed in the European Patent Application Publication No. 0055206 discussed above are overcome.
A fourth detouring press nip No is formed between the smooth-faced rock roll 43 and a press roll 52 having a hollow face 53. A conventional press felt 50 runs through the fourth press nip No guided by guide rolls 51. The felt 50 is reconditioned by conventional felt reconditioning means OWE
It is apparent from the foregoing that in the first nip No, detouring of the web occurs substantially symmetrically through both faces of the web. In-the second nip No, detouring takes place substantially entirely in a first direction towards the second felt 30 through only that face of the web which contacts the second felt since the belt felt 40 is substantially water non receiving. As noted above, the third nip No functions as a smoothing and transfer nip since there are no water-receiving fabrics which pass there through. In the fourth nip No, detouring takes place in a second direction towards the press felt 50, i.e., in a direction opposite from the first direction of detouring in the second nip No. In this manner, an efficient and substantially symmetrical detouring is ensured in addition to a symmetrical distribution of fines and filler agents within the web. This is important especially in the case of fine paper grades for the production of which the press section of the present invention is mainly intended The belt felt 40 may, for example, be constructed of mesh-like reinforcement fabric which provides good resistance to tension. The fabric is preferably impregnated with plastic, rubber or a similar material.
By appropriate selection of the properties of the face of the belt felt 40 that contacts the web W, it is possible to affect the properties of one face of the web and in particular its smoothness in a predictable manner as will be understood by those skilled in the art. Although the belt felt 40 may be to at least some lo extent water-receiving and even slightly air permeable, the permeability of the belt felt I has no essential significance. It will be understood that it is the properties of the surface of the belt felt 40 which contacts the web W and, in particular, the smoothness of this surface and the adhesion properties of the surface relative to the web which are important. These properties must be such as to reliably ensure that the web will follow the belt felt 40 after the second nip No, i.e., will become detached from the press felt 30.
After the last nip No, the web is detached from the smooth face 44 of the rock roll 43 by means of a guide roll 560 The face 44 of rock roll 43 is kept clean by means of a doctor 45.
After the press section, the web W is passed to a conventional drying section which includes a lead-in cylinder 62, a drying cylinder 63 of an upper line of cylinders, and a drying cylinder 64 of a lower line of drying cylinders. The web W is transferred onto a support fabric 60 as it travels over cylinder 62, the fabric 60 being guided by guide roll 61.
Obviously, numerous modifications and variations of the present invention are possible in the light of the above teachings It is therefore to be understood that within the scope of the claims appended hereto the invention may be practiced otherwise than as specifically disclosed herein.
Claims (12)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS
FOLLOWS:
1. In a press section for a paper machine including at least four successive nips between which the web from which water is drained runs as a closed draw supported on at least one of a fabric and roll face, without open draw, and in which press section the web is dewatered substantially symmetrically through both faces of the web, the press section including a first fabric which functions as a pick up felt and onto a lower face of which the web adheres, a first dewatering press nip formed between a first pair of press rolls into which the web is carried by said first fabric which comprises an upper fabric in the first dewatering press nip, a second fabric comprising a lower felt in said first dewatering press nip, a second nip formed between a second pair of upper and lower rolls and into which the web is carried by said second fabric, a third substantially non-dewatering smoothing and transfer nip formed between said upper roll of said second nip and a smooth-faced roll, the web being detached from said second fabric after passing through said second nip to follow along with said upper roll of said second nip into said third nip, a fourth dewatering nip formed between said smooth-faced roll and a dewatering press roll, a press felt passing through said fourth dewatering nip, and wherein said first, second, third and fourth nips are arranged such that in said first nip dewatering takes place through both faces of the web, in said second nip dewatering takes place in a first direction through only the one face of the web which contacts said second fabric which carries the web into said second nip, and in said fourth nip dewatering takes place in a second direction opposite from said first direction, the improvement comprising:
a belt felt runs over a sector of the face of said upper roll of said second nip between and through said second and third nips, said belt felt being substantially water non-receiving and having a smooth-faced outer surface having surface properties such that the web is detached from said second fabric after passing through said second nip and adheres to said belt felt and is supported thereon, said belt felt transferring the web into said third substantially non-dewatering smoothing and transfer nip, whereupon the web becomes detached from said belt felt at least in part due to the surface properties thereof and adheres to said smooth-faced press roll of the third nip on the face of which the web is carried into said fourth press nip.
a belt felt runs over a sector of the face of said upper roll of said second nip between and through said second and third nips, said belt felt being substantially water non-receiving and having a smooth-faced outer surface having surface properties such that the web is detached from said second fabric after passing through said second nip and adheres to said belt felt and is supported thereon, said belt felt transferring the web into said third substantially non-dewatering smoothing and transfer nip, whereupon the web becomes detached from said belt felt at least in part due to the surface properties thereof and adheres to said smooth-faced press roll of the third nip on the face of which the web is carried into said fourth press nip.
2. The combination of claim 1 wherein said belt felt is formed of a substantially water non-receiving and water impervious fabric structure.
3. The combination of claim 2 wherein said belt felt is formed of a mesh-like reinforcement fabric, said fabric being impregnated with a water impervious material.
4. The combination of claim 3 wherein said mesh-like reinforcement fabric of said belt felt is formed of yarn-like members, said fabric being impregnated with a plastic-like material.
5. The combination of claim 1 wherein said first pair of press rolls forming said first detouring press nip include a lower press suction roll provided with a suction zone and an upper hollow-faced press roll.
6. The combination of claim 1 wherein said lower roll of said second nip is a hollow-faced press roll and said upper roll of said second nip is a solid-mantle press roll.
7. The combination of claim 6 wherein said upper roll of said second nip is a smooth-faced solid-mantle press roll.
The combination of claim 6 wherein said upper roll of said second nip is a hollow-faced solid mantle press roll.
9. The combination of claim 1 wherein said belt felt is separated from said face of said upper roll of said second nip after passing through said third nip and is guided thereafter by guide rolls.
10. The combination of claim 1 wherein said first and second nips are substantially horizontal nips, said second fabric and web supported thereby have a substantially horizontal run between said first and second nips, and wherein the web adheres to the outer surface of said belt felt after passing through said second nip and follows along said belt felt over said sector of said face of said upper roll of said second nip.
11. The combination of claim 10 wherein said sector defines a central angle having a magnitude in the range of between about 90° to 180°.
12. The combination of claim 11 wherein said central angle has a magnitude in the range of between about 120° to 150°.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FI831577 | 1983-05-06 | ||
| FI831577A FI71370C (en) | 1983-05-06 | 1983-05-06 | SLUTET PRESSPARTI I PAPPERSMASKIN |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1232162A true CA1232162A (en) | 1988-02-02 |
Family
ID=8517162
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000453481A Expired CA1232162A (en) | 1983-05-06 | 1984-05-03 | Press section for a paper machine |
Country Status (4)
| Country | Link |
|---|---|
| CA (1) | CA1232162A (en) |
| DE (1) | DE3415457A1 (en) |
| FI (1) | FI71370C (en) |
| SE (1) | SE461918B (en) |
Families Citing this family (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE4321406A1 (en) * | 1993-06-26 | 1993-11-11 | Voith Gmbh J M | Paper-making press section - has belt round first two rollers working with press rollers and shoe press for high water extraction and no difference between paper sides |
| DE19543111C2 (en) * | 1995-11-18 | 2001-01-25 | Voith Sulzer Papiermasch Gmbh | Press section of a paper machine with closed web guidance and method for dewatering a paper web |
| DE10251666A1 (en) * | 2002-11-06 | 2004-06-03 | Voith Paper Patent Gmbh | Press arrangement |
| DE10342733A1 (en) * | 2003-09-16 | 2005-04-21 | Voith Paper Patent Gmbh | Press section to extract water from a wet web, of paper or cardboard or tissue, has an impermeable transfer belt around the first press roller to pass the web on to the next station without web damage |
| AT504090B1 (en) * | 2006-09-13 | 2008-09-15 | Andberg Janne Johannes | INTERMEDIATE TILTING ARRANGEMENT OF A DRAINAGE DEVICE WITH A TISSUE-CONVERSED OVERRIDE OVER ROLLER |
Family Cites Families (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FI751754A (en) * | 1975-06-12 | 1976-12-13 | Valmet Oy | |
| FI770542A (en) * | 1977-02-18 | 1978-08-19 | Valkama P J | PRESS RELEASE FOR THE CONSTRUCTION OF VAT ON FIBER BAN |
| DE2751245A1 (en) * | 1977-11-16 | 1979-06-21 | Valmet Oy | paper making pressing section exploiting viscosity of heated water - feeds steam and ensures heat retention by web and felt |
| FI79731C (en) * | 1980-12-18 | 1990-02-12 | Beloit Corp | Press section of a paper machine |
| FI822425L (en) * | 1982-07-07 | 1984-01-08 | Valmet Oy | PROCEDURE FOR THE PRESS RELEASE OF THE PRESS RELEASE OF THE FIBER, THE SYNNER AND THE PAPER-ELLER |
-
1983
- 1983-05-06 FI FI831577A patent/FI71370C/en not_active IP Right Cessation
-
1984
- 1984-04-25 DE DE19843415457 patent/DE3415457A1/en not_active Withdrawn
- 1984-05-03 CA CA000453481A patent/CA1232162A/en not_active Expired
- 1984-05-04 SE SE8402403A patent/SE461918B/en not_active IP Right Cessation
Also Published As
| Publication number | Publication date |
|---|---|
| SE461918B (en) | 1990-04-09 |
| SE8402403D0 (en) | 1984-05-04 |
| FI71370B (en) | 1986-09-09 |
| FI831577L (en) | 1984-11-07 |
| FI71370C (en) | 1986-12-19 |
| DE3415457A1 (en) | 1984-11-15 |
| FI831577A0 (en) | 1983-05-06 |
| SE8402403L (en) | 1984-11-07 |
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| Date | Code | Title | Description |
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| MKEX | Expiry |