The present invention relates to a method for the production of a fibrous web. It moreover relates in particular to a machine, suitable for the implementation of such a method for the production of a fibrous web.
To date, no tool is available for direct control or adjustment of the transverse elongation characteristics (CD elasticity) of paper. The shrinkage curve resulting in the transverse direction, or CD shrinkage profile (CD=cross direction), still firmly specifies these transverse elongation characteristics as the result of paper drying. Thus, the papermaker so far only has the possibility to influence the CD elasticity or the CD shrinkage profile at the expense of the web stabilization via web stabilization boxes, which is not a satisfactory measure. The machine builder can somewhat influence the CD shrinkage profile via the drying concept, such as in particular a single-row or double-row dryer section. However, compromises also have to be made here.
Reduced elongation characteristics or insufficient elasticity have a particularly negative effect on corrugated raw material. For example, the corrugated cardboard can break during corrugating, rendering it unusable as scrap. A brittle corrugated cardboard box will burst under impact because the impact energy cannot be absorbed. In addition, when producing the corrugation from the corrugating medium, the web can break if the elasticity is too low when corrugating with the corrugating roll. Too much brittleness is therefore also counterproductive here.
The well-known Clupak system is used for the targeted adjustment of a longitudinal elongation of paper (MD elasticity, MD=machine direction, machine running direction) or for producing a longitudinally directed micro crepe. Therein, the still moist web runs together with a rubber blanket through a press nip, whereby both are stretched. After the nip, the cloth contracts again, and the desired micro-creping is achieved in the web.
What is needed in the art is a method and a machine of the type described at the beginning, with which the aforementioned disadvantages can be eliminated. What is needed in the art is in particular to be able to specifically control or adjust or to improve the resulting elasticity or the transverse elongation characteristic and the energy absorption of the fibrous web in the transverse direction. What is also needed in the art is to create a possibility of counteracting the increasingly declining quality of waste paper raw material.
The present invention relates to a method for the production of a fibrous web which can be elongated in transverse direction. It moreover relates in particular to a machine, suitable for the implementation of such a method for the production of a fibrous web that can be elongated in the transverse direction.
The present invention provides a method for producing a fibrous web which can be elongated in the transverse direction, in particular a paper or cardboard web which can be elongated in the transverse direction, is characterized in that the fibrous web exiting a pre-drying section of the particular production machine is brought into contact with a heated rotating cylinder which is smooth and impermeable to steam, and the fibrous web is guided over the heated cylinder together with a circulating elastic belt which is impermeable to steam over a specified or specifiable angle of wrap so as to be positioned between the elastic belt and the heated cylinder—that is, the cylinder surface, —and is pressed against the cylinder by the elastic belt; the elastic belt is subjected to a variably adjustable and/or controllable pre-tensioning in the transverse direction before being brought into contact with the fibrous web, and the pre-tensioning of the elastic belt generated in transverse direction is relieved again after formation of a steam cushion between the fibrous web and the heated cylinder, so that the fibrous web is shrunk with the elastic belt in the transverse direction in a sliding manner over the steam cushion on the heated cylinder.
With such an embodiment of the method according to the present invention, the elasticity or respectively the transverse elongation characteristic resulting in transverse direction and the energy absorption of the fibrous web in the transverse direction can now be controlled or adjusted or improved in a targeted manner. Moreover, the possibility is created to counteract the increasingly declining waste paper raw material quality. The fibrous web coming from the pre-dryer section runs onto the elastic belt which is pre-tensioned in the transverse direction. By relieving the pre-tension of the elastic belt after the formation of the steam cushion between the fibrous web and the heated cylinder, the fibrous web can shrink in the transverse direction over the steam cushion on the heated cylinder, sliding with the elastic belt to produce the micro-crepe.
A steel cylinder, in particular a chrome-plated steel cylinder, is optionally used as the heated cylinder. Such a steel cylinder, in particular a chrome-plated steel cylinder, ensures that the fibrous web can slide optimally on it after formation of the steam cushion.
The elastic belt is advantageously pre-tensioned in transverse direction by at least one variably adjustable tension roller arranged inside its loop.
With the pre-tensioning in transverse direction being variably adjustable via the tension roll, the transverse shrinkage resulting after a reduction in the pre-tension can be controlled or adjusted accordingly.
The pre-tensioning of the elastic belt which is generated in transverse direction is advantageously relieved again between a variably adjustable tension roll arranged inside the loop of the elastic belt and a guide roll arranged inside the loop of the elastic belt, viewed in direction of web travel.
Since, the elastic belt traveling over the guide roll is subjected to minimal or no pretension in the region of this guide roll, its pretension between the tension roll and this guide roll can again decrease continuously.
According to an optional practical embodiment of the method according to the invention—in particular for relatively lower machine or web speeds, optionally for machine or web speeds of <1000 m/min—the steam cushion between the fibrous web and the heated cylinder is generated in a press nip which is provided in the initial area of the zone of the heated cylinder around which the fibrous web and the elastic belt viewed in direction of web travel are looped; said press nip is formed between the heated cylinder and a press roll arranged inside the loop of the elastic belt, which is designed at the same time as a variably adjustable tension roller by way of which the elastic belt is pre-tensioned in transverse direction.
Since the initial press roll provided for forming a steam cushion between the fibrous web and the heated cylinder is at the same time designed as a variable adjustable tension roll, the respective desired pretension in transverse direction can be imposed on the elastic belt.
It is herein especially advantageous if—viewed in direction of web travel—a guide roll holding the elastic belt and the fibrous web on the heated cylinder is provided inside the loop of the elastic belt in the rear area of the zone of the heated cylinder around which the fibrous web and the elastic belt are wrapped, so that the pre-tensioning of the elastic belt that was generated in transverse direction is already relieved between the press nip provided in the initial region of the zone of the heated cylinder around which the fibrous web and the elastic belt are wrapped —when viewed in direction of web travel—and the guide roll provided in the rear region of the zone of the heated cylinder around which, viewed in direction of web travel, the fibrous web and the elastic belt are wrapped for generating transverse shrinkage of the fibrous web.
The elastic belt is herein again removed advantageously from the heated cylinder via the guide roll provided in the rear area of the zone of the heated cylinder around which the fibrous web and the elastic belt are wrapped, as viewed in direction of web travel, and the fibrous web is separated again from the elastic belt.
According to an optional practical embodiment of the method according to the invention, in particular for relatively higher machine or web speeds, optionally for machine or web speeds of >1000 m/min, the fibrous web together with the pretensioned elastic belt is guided—for the purpose of forming the steam cushion between the fibrous web and the heated cylinder—along a conditioning or warm-up zone over the heated cylinder with the elastic belt maintained in pretensioned condition.
Thus, in this case, the steam cushion is formed in the region of the conditioning and warm-up zone.
It is therein particularly advantageous if the elastic belt is fed to the fibrous web that is brought into contact with the heated cylinder via a variably adjustable tensioning roll which pretensions the fibrous web, and if in order to increase the adhesion of the fibrous web to the elastic belt at the end of the conditioning or warm-up zone a press nip is provided which is formed between the heated cylinder and a press roll arranged within the loop of the elastic belt, which, for maintaining the pretension of the elastic belt within the preceding conditioning or warm-up zone, is at the same time designed as a variably adjustable tension roll; and the fibrous web, following the press nip provided at the end of the conditioning or warm-up zone, is guided together with the elastic belt along a shrinkage zone further over the heated cylinder, along which the pretension of the elastic belt is again relieved for producing the transverse shrinkage of the fibrous web.
The press nip provided at the end of the conditioning or warm-up zone thus ensures good adhesion between the fibrous web and the pretensioned elastic belt. While the fibrous web now adheres securely to the elastic belt, the existing steam cushion continues to ensure full mobility of the fibrous web relative to the heated cylinder.
The fibrous web together with the elastic belt is thereby advantageously fed to a guide roll following the shrinkage zone, via which the fibrous web and the elastic belt are again removed from the heated cylinder and separated from each other.
By way of a respective guide roll, the elastic belt can still be subjected to a basic tension that, compared to the pretension, is lower by a defined amount.
The fibrous web which was shrunk in transverse direction is optionally fed to an after-drying section of the production machine, where the transverse-shrinkage is set.
The machine according to the invention, which is particularly suitable for implementation of the method according to the invention, for producing a fibrous web which can be elongated in the transverse direction, in particular a paper or cardboard web which can be elongated in transverse direction, is characterized in that it includes a heated steam impermeable, smooth rotating cylinder and an elastic belt which is impermeable to steam, wherein the fibrous web is guided together with the elastic belt over a specified or specifiable wrapping angle between the elastic belt and the heated cylinder, positioned above the heated cylinder, and pressed against the latter by the elastic belt; the elastic belt can be subjected to a variably adjustable and/or controllable pretension in transverse direction before being brought into contact with the fibrous web, and the pretension of the elastic belt generated in transverse direction can be relieved after formation of a steam cushion between the fibrous web and the heated cylinder, so that the fibrous web shrinks with the elastic belt in the transverse direction in a sliding manner over the steam cushion on the heated cylinder.
A steel cylinder, in particular a chrome-plated steel cylinder, is optionally used as the heated cylinder.
The elastic belt can advantageously be pre-tensioned in transverse direction by at least one variably adjustable tension roller arranged inside its loop.
It is thereby particularly advantageous if the pre-tensioning of the elastic belt which is generated in transverse direction is relieved again between a variably adjustable tension roll arranged inside the loop of the elastic belt and a guide roll arranged inside the loop of the elastic belt, viewed in direction of web travel.
According to an optional practical embodiment of the machine according to the invention—in particular for relatively lower machine or web speeds, optionally for machine or web speeds of <1000 m/min—the steam cushion between the fibrous web and the heated cylinder is generated in a press nip which is provided in the initial area of the zone of the heated cylinder around which the fibrous web and the elastic belt viewed in direction of web travel are looped; said press nip is formed between the heated cylinder and a press roll arranged inside the loop of the elastic belt, which is designed at the same time as a variably adjustable tension roller by way of which the elastic belt is pre-tensioned in transverse direction.
It is herein especially advantageous if—viewed in direction of web travel—a guide roll holding the elastic belt and the fibrous web on the heated cylinder is provided inside the loop of the elastic belt in the rear area of the zone of the heated cylinder around which the fibrous web and the elastic belt are wrapped, so that the generated transverse directional pretension of the elastic belt is already relieved between the press nip provided in the initial region of the zone of the heated cylinder around which the fibrous web and the elastic belt are wrapped—when viewed in direction of web travel—and the guide roll provided in the rear region of the zone of the heated cylinder around which, viewed in direction of web travel, the fibrous web and the elastic belt are wrapped for generating transverse shrinkage of the fibrous web.
The elastic belt is herein again removed advantageously from the heated cylinder via the guide roll provided in the rear area of the zone of the heated cylinder around which the fibrous web and the elastic belt are wrapped, as viewed in direction of web travel, and the fibrous web is separated again from the elastic belt.
According to an optional practical embodiment of the machine according to the invention, in particular for relatively higher machine or web speeds, optionally for machine or web speeds of >1000 m/min, the fibrous web together with the pretensioned elastic belt is guided—for the purpose of forming the steam cushion between the fibrous web and the heated cylinder—along a conditioning or warm-up zone over the heated cylinder with the elastic belt maintained in pretensioned condition.
It is therein particularly advantageous if the elastic belt can be fed to the fibrous web that is brought into contact with the heated cylinder via a variably adjustable tensioning roll which pretensions the fibrous web, and if in order to increase the adhesion of the fibrous web to the elastic belt at the end of the conditioning or warm-up zone a press nip is provided which is formed between the heated cylinder and a press roll arranged within the loop of the elastic belt, which, for maintaining the pretension of the elastic belt within the preceding conditioning or warm-up zone, is at the same time designed as a variably adjustable tension roll; and the fibrous web, following the press nip provided at the end of the conditioning or warm-up zone, is guided together with the elastic belt along a shrinkage zone further over the heated cylinder, along which the pretension of the elastic belt can again be relieved for producing the transverse shrinkage of the fibrous web.
The fibrous web together with the elastic belt is thereby advantageously fed to a guide roll following the shrinkage zone, via which the fibrous web and the elastic belt are again removed from the heated cylinder and separated from each other.
By way of a respective guide roll, the elastic belt can still be subjected to a basic tension that, compared to the pretension, is lower by a defined amount.
Advantageously, the pre-tensioning of the elastic belt can be adjusted via tensioning devices provided laterally on the roll body of a respective tensioning roll and variably adjustable in transverse machine direction relative to the roll body.
According to an optional practical embodiment of the machine according to the invention, the elastic belt—for the purpose of targeted manipulation of the elongation of the fibrous web in the transverse direction—is provided symmetrically to its central longitudinal axis parallel to the machine direction with reinforcing threads extending at least substantially in transverse direction with correspondingly adapted elasticity moduli or with a laid scrim correspondingly adapted in particular with regard to its thread density.
It is thereby also particularly advantageous if the elasticity moduli of the reinforcing threads extending in transverse direction or the laid scrim of the elastic belt are or is correspondingly adapted to compensate for the trough-shaped shrinkage curve normally occurring in transverse direction during drying of the fibrous web.
The elastic belt may moreover also be provided with reinforcing threads extending at least substantially in the machine direction.
The elastic belt consists advantageously at least substantially of rubber.
The elastic belt has optionally a hardness of 55+/−10 Shore (107 P&J).
It is also advantageous if the elastic belt has a density in the range of approximately 1.2 kg/dm3 to approximately 1.5 kg/dm3.
The elastic belt has optionally a thickness in the range of approximately 20 mm to approximately 30 mm, whereby a thickness of approximately 25 mm is optional.
Additional advantageous embodiments of the machine according to the invention are characterized in that
The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein:
Corresponding reference characters indicate corresponding parts throughout the several views. The exemplification set out herein illustrate embodiments of the invention, and such exemplifications are not to be construed as limiting the scope of the invention in any manner.
Machines 10 always include a heated, steam-impermeable and smooth rotating cylinder 14, and a steam-impermeable circulating elastic belt 16.
In each case, fibrous web 12 is guided over heated cylinder 14 together with elastic belt 16 at a specified or specifiable wrap angle between elastic belt 16 and heated cylinder 14 and is pressed against the latter by elastic belt 16.
Elastic belt 16 can be subjected to a variably adjustable and/or controllable pretension in transverse direction before being brought into contact with fibrous web 12. The pretension of elastic belt 16 generated in transverse direction can be relieved again after formation of a steam cushion between fibrous web 12 and heated cylinder 14, so that fibrous web 12 shrinks with the elastic belt in transverse direction in a sliding manner over the steam cushion on heated cylinder 14.
In machine 10, illustrated in
Viewed in direction of web travel I, a guide roll 22 holding elastic belt 16 and fibrous web 12 on heated cylinder 14 is provided inside the loop of elastic belt 16 in the rear area of the zone of heated cylinder 14 around which fibrous web 12 and elastic belt 16 are wrapped, so that the generated pretension generated in the transverse direction of elastic belt 16 is already relieved between press nip 18 provided in the initial region of the zone of heated cylinder 14 around which fibrous web 12 and elastic belt 16 are looped—when viewed in direction of web travel I—and guide roll 22 provided in the rear region of the zone of heated cylinder 14 around which, viewed in direction of web travel I, fibrous web 12 and elastic belt 16 are wrapped for generating transverse shrinkage of fibrous web 12.
Elastic belt 16 is again removed from heated cylinder 14 via guide roll 22 provided in the rear area of the zone of heated cylinder 14 around which fibrous web 12 and elastic belt 16 are wrapped, as viewed in direction of web travel I, and fibrous web 12 is separated again from elastic belt 16.
In contrast, in machine 10 according to
Elastic belt 16 of fibrous web 12 that is brought into contact with heated cylinder 14 is fed via a variably adjustable tensioning roll 24 which pretensions fibrous web 12. In order to increase the adhesion of fibrous web 12 to elastic belt 16 at the end of the conditioning or warm-up zone α, a press nip 26 is provided which is formed between the cylinder 16 and a press roll 28 arranged within the loop of elastic belt 16, which, for maintaining the pretension of elastic belt 16 within the preceding conditioning or warm-up zone α, is at the same time designed as a variably adjustable tension roll. Fibrous web 12 following press nip 26 provided at the end of conditioning or warm-up zone α, is guided together with elastic belt 16 along a shrinkage zone β further over heated cylinder 14, along which the pretension of elastic belt 16 can again be relieved for producing the transverse shrinkage of fibrous web 12.
Following shrinkage zone β, fibrous web 12 together with elastic belt 16 is fed to a guide roll 30, via which fibrous web 12 and elastic belt 16 are again removed from heated cylinder 14 and separated from each other.
In the two embodiment examples according to
As can be seen from
In contrast,
In both
An exemplary progression of elasticity moduli E of the reinforcing threads provided symmetrically relative to central longitudinal axis L of elastic belt 16 according to
As already mentioned, the continuous line in
While this invention has been described with respect to at least one embodiment, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.
Number | Date | Country | Kind |
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10 2020 114 602.7 | Jun 2020 | DE | national |
This is a continuation of PCT application no. PCT/EP2021/053810, entitled “METHOD AND MACHINE FOR PRODUCING A FIBROUS WEB WHICH CAN BE ELONGATED IN THE TRANSVERSE DIRECTION”, filed Feb. 17, 2021, which is incorporated herein by reference. PCT application no. PCT/EP2021/053810 claims priority to German patent application no. DE 10 2020 114 602.7, filed Jun. 2, 2020, which is incorporated herein by reference.
Number | Date | Country | |
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Parent | PCT/EP2021/053810 | Feb 2021 | US |
Child | 18073684 | US |