Web stabiliser and method for forming a negative pressure

Abstract

The invention relates to a web stabiliser (1) for a machine for producing a fibre material web and is characterised in that end-face sealing against a covering (3) is provided either by a sealing element (6) or by a further sealing element (8) which can be moved against the covering (3). The invention permits an advantageous and in particular energy-efficient forming of a negative pressure in the application region of the web stabiliser (1).

Description

[0001] Web stabilizer and method for creating a negative pressure

[0002] The invention relates to a web stabilizer for creating a negative pressure in a pocket space formed between a deflection roller and a fabric of a machine for producing a fibrous web, comprising a seal for sealing an end face of the pocket space and in particular for sealing the end face of a gusset formed between the deflection roller and the fabric, wherein the seal comprises a sealing element for sealing the end face against the fabric. The invention also relates to a method for creating a negative pressure in a pocket space formed between a deflection roller and a fabric of a machine for producing a fibrous web.

[0003] In a machine for producing a fibrous web, and particularly in a drying section of such a machine, effective guidance of the fibrous web is essential. For this purpose, the fibrous web is guided at least sectionally on a clothing through the machine or the drying section. The use of web stabilizers, which are designed to create a negative pressure in a pocket space formed between a deflection roller and a clothing, allows stable removal of the fibrous web from a drying cylinder onto the clothing, as well as stable guidance of the fibrous web on the clothing up to the deflection roller. In particular, this reduces tension on the fibrous web and lowers the risk of the fibrous web breaking. A high negative pressure in the pocket space is particularly advantageous, which is why effective sealing of the pocket space between the deflection roller and the clothing is important.Generally, web stabilizers are used in single-row as well as double-row dryer groups.

[0004] EP 1 788 153 A2 discloses a device for treating a material web with a stabilizer, which comprises a sealing device configured essentially in the cross-machine direction, i.e., along a main axis of the stabilizer, for sealing a take-off zone. Additionally, a lateral seal of the take-off zone, i.e., at the end faces of the take-off zone, is provided via a Teflon seal. The Teflon seal can be pivoted out of the predetermined sealing position via a cylinder / piston unit when a predetermined load is exceeded, for example, due to the occurrence of web thickening or the like.

[0005] Due to the pivoting bearing, the Teflon seal can pivot accordingly if a paper jam occurs, for example.

[0006] The aim of the invention is a web stabilizer that allows effective sealing of the front side of the covering under different operating conditions.

[0007] This is achieved according to the invention in that the seal comprises a movable, further sealing element for sealing the front side against the clothing, wherein the front side sealing against the clothing is provided either via the sealing element or via the further sealing element that is movable against the clothing. The sealing element allows a front side sealing of the pocket space and in particular of a gusset formed between the deflection roller and the clothing, wherein the sealing is effected against the clothing. The inventor recognized that the requirements for sealing against the clothing depend heavily on the operating state of the machine. For example, a first operating state of the machine can be characterized by operation with a fibrous web guided on the clothing. Alternatively, a further operating state of the machine can be characterized by operation without a fibrous web guided on the clothing.The permeability strongly depends on whether a fibrous web is guided on the clothing or not. In particular, in the case of a developed negative pressure, the deflection of the clothing, for example, guided from a drying cylinder to a deflection roll, is strongly dependent on the permeability, with lower permeability implying a greater deflection. Especially during operation with a fibrous web guided on the clothing, a strong deflection of the clothing in the direction of the negative pressure occurs. Similarly, during operation without a fibrous web guided on the clothing, a small or negligible deflection is to be expected.

[0008] It was thus recognized that the sealing element effectively seals the front end against the clothing, particularly for a first operating state of the machine. The sealing element has a contour relative to the clothing, and the contour of the sealing element is designed according to the expected contour of the clothing, i.e., according to the first operating state, in particular operation with a fibrous web guided on the clothing. On the one hand, there are empirical values ​​here, and on the other hand, a sealing element wears in accordingly, whereby a ground-in sealing element allows the expert to draw conclusions regarding a preferred contour.According to the invention, the seal comprises a further movable sealing element for front-end sealing against the clothing, wherein the further sealing element has a further contour relative to the clothing corresponding to a further operating state of the machine. The invention thus allows front-end sealing against the clothing either via the sealing element or via the further sealing element movable relative to the clothing, wherein the further sealing element enables effective sealing particularly in the case of the further operating state. The further sealing element has a further contour relative to the clothing. The further contour of the further sealing element is to be designed according to the expected contour of the clothing, i.e. according to the further operating state, in particular according to operation without a fibrous web guided on the clothing.Consequently, the invention allows for effective end-face sealing in the first operating state via the sealing element and in the further operating state via the further sealing element. In particular, this minimizes the gap between the covering and the sealing element or the further sealing element, while simultaneously preventing contact between the surrounding covering and the sealing element. This allows for the greatest possible negative pressure to be achieved with minimal energy expenditure, regardless of the operating state, and prevents wear on the covering or the sealing element and the associated follow-up costs.

[0009] In an advantageous embodiment of the web stabilizer, a movement means for moving the further sealing element against the clothing, in particular a pneumatic cylinder, a hydraulic cylinder or an actuator, is assigned to the further sealing element. The movement means allows the further sealing element to be guided against the clothing for end-face sealing or away from the clothing. In particular, when the first operating state is present, i.e. operation with a fibrous web guided on the clothing, the further sealing element can be guided away from the more strongly deflected clothing, with the end-face sealing being effected via the sealing element. Conversely, when the further operating state is present, i.e. operation without a fibrous web guided on the clothing, the further sealing element is guided against the barely deflected clothing and the end-face sealing is effected via the further sealing element.

[0010] Advantageously, the additional sealing element is guided in a guide and can be guided against the covering via the movement means. Particularly advantageously, the guide comprises two elongated holes in the additional sealing element, wherein the additional sealing element is guided in the elongated holes via guide pins, and the guide pins are connected to the web stabilizer and in particular to the sealing element. By guiding the additional sealing element, the additional sealing element can be positioned in clearly defined positions relative to the covering. In particular, guiding via elongated holes allows two clearly defined positions to be very easily defined, whereby these positions are achieved via the respective end positions in the elongated holes.

[0011] Advantageously, the movement means is connected on the one hand to the track stabilizer and on the other hand to the further sealing element, which enables a very compact design and exact relative positioning.

[0012] Likewise advantageously, the sealing element and the additional sealing element are arranged parallel, in particular flush, and offset from one another. This allows, in particular, a simple relative arrangement or positioning of the sealing element to the additional sealing element.

[0013] In a further advantageous embodiment of the web stabilizer, the sealing element has a contour opposite the fabric, wherein the contour is substantially curved for sealing the front face against the fabric. The contour of the sealing element is designed according to the expected contour of the fabric, i.e., according to the first operating state, in particular operation with a fibrous web guided on the fabric. The sealing element designed in this way allows for effective sealing at the front face against the more strongly deflected fabric, while maintaining a minimal gap between the fabric and the sealing element.

[0014] In an equally advantageous embodiment of the web stabilizer, the additional sealing element has a further contour opposite the clothing, wherein the further contour is essentially designed as a straight line for the end-face sealing against the clothing. The additional sealing element has a further contour opposite the clothing depending on the further operating state of the machine, in particular, depending on operation without a fibrous web guided on the clothing. This allows for effective end-face sealing against the negligibly deflected clothing, since a minimal gap is realized between the clothing and the sealing element even during operation according to the further operating state.

[0015] In an equally advantageous embodiment of the web stabilizer, the sealing element and / or the additional sealing element is also designed to seal against the deflection roller, and the web stabilizer is designed, in particular, to suction the deflection roller. Since the arrangement of the sealing element can remain unchanged in both the first and the further operating state, and thus remains unchanged relative to the deflection roller, the sealing element can also be designed to match the contour of the deflection roller for end-to-end sealing against the deflection roller, ensuring a minimal gap between the sealing element and the deflection roller. Sealing against the deflection roller is also possible via the additional movable sealing element. For this purpose, the additional sealing element also has a contour corresponding to the deflection roller and is advantageously moved along the circumference of the deflection roller, maintaining a minimal gap.The web stabilizer also advantageously allows for suction to be applied to the deflection roller, whereby the deflection roller is designed as a suction roller, i.e., with openings along its circumference. This allows for very easy suction to the deflection roller and enables a cost-effective and space-saving design.

[0016] In a further advantageous embodiment of the web stabilizer, the sealing element and / or the additional sealing element are made of a plastic, in particular polytetrafluoroethylene. Upon contact of the covering with the sealing element or the additional sealing element, the plastic allows for grinding or adjustment of the contour or the additional contour, whereby the covering is subject to negligible wear. In an equally advantageous embodiment of the web stabilizer, the sealing element is detachably connected to the web stabilizer, in particular via a screw connection. This allows for easy replacement of the sealing element or even simple replacement of the sealing element to optimize the contour.

[0017] In a further advantageous embodiment of the web stabilizer, the sealing element is designed to be movable relative to the web stabilizer for retraction from the gusset. This allows the sealing element to be moved into a service position, thereby improving machine accessibility for service personnel.

[0018] A drying group of a machine for producing a fibrous web is particularly advantageous, comprising a deflection roller which can be vacuumed in particular via the web stabilizer, a drying cylinder and a web stabilizer according to the invention, wherein a clothing, in particular a drying fabric, is guided around the deflection roller and the drying cylinder, wherein the web stabilizer - and in particular the seal for sealing the end face - is arranged in the pocket space formed between the deflection roller and the clothing. Different operating states occur during operation of the drying group. For example, in a first operating state, the fibrous web is guided on the clothing and in a second operating state, however, no fibrous web is guided on the clothing.The drying group can be operated optimally in both the first and second operating modes, since the advantageous frontal sealing enables optimal development of the negative pressure in every operating mode.

[0019] The invention also relates to a method for forming a negative pressure in a pocket space formed between a deflection roller and a fabric of a machine for producing a fibrous web, wherein the fabric is guided around the deflection roller and a drying cylinder and the pocket space is at least partially vacuumed via a web stabilizer according to the invention, wherein in a first operating state of the machine, in particular in a state with a fibrous web guided on the fabric, the end-side sealing against the fabric is effected via the sealing element, and when changing from the first operating state of the machine to a second operating state of the machine, in particular to a state without a fibrous web guided on the fabric, the further sealing element is moved against the fabric,In the second operating state of the machine, the end-face seal against the clothing is achieved via the additional sealing element. As already explained with regard to the web stabilizer according to the invention, an advantageous end-face seal can be achieved in both the first and second operating states, independent of the operating state, thus providing an optimally formed vacuum.

[0020] In a particularly advantageous embodiment of the method according to the invention, the machine for producing the fibrous web comprises a sensor for detecting the fibrous web on the fabric. If the absence of the fibrous web on the fabric is detected, the further sealing element is moved against the fabric. In particular, the sensor is arranged in a drying group of the machine. Advantageously, the sensor allows the automated movement of the further sealing element, wherein in the first operating state of the machine with the fibrous web guided on the fabric, the further sealing element is not guided against the fabric, and wherein in the second operating state of the machine without a fibrous web guided on the fabric, the further sealing element is guided against the fabric.

[0021] The invention will now be described by way of example with reference to the drawings.

[0022] Fig. 1 shows an arrangement of a web stabilizer in a single-row dryer group according to the state of the art.

[0023] Fig. 2 shows an arrangement of a web stabilizer in a two-row dryer group according to the state of the art.

[0024] Fig. 3 shows a web stabilizer according to the invention in a first operating state.

[0025] Fig. 4 shows the web stabilizer according to the invention in a second operating state.

[0026] Fig. 5 shows the web stabilizer according to the invention with a retracted seal. Fig. 1 shows an arrangement of a web stabilizer 1 in a single-row drying group of a machine for producing a fibrous web according to the prior art. A clothing 3 is guided between a drying cylinder 12 and a deflection roller 2, which is designed in particular as a suction roller, wherein the web stabilizer 1 is arranged to create a negative pressure in the pocket space 4 formed between the deflection roller 2 and the clothing 3. The fibrous web is guided between the drying cylinder 12 and the clothing 3, wherein the web stabilizer 1 enables reliable removal from the drying cylinder 12 onto the clothing 3, as well as reliable guidance of the fibrous web on the clothing 3 to the deflection roller 2.In the case of the deflection roller 2 designed as a suction roller, the fibrous web is fixed on the fabric 3, whereby the deflection roller 2 can be suctioned via the web stabilizer 1.

[0027] Fig. 2 shows an arrangement of a web stabilizer 1 in a two-row dryer group of a machine for producing a fibrous web according to the prior art. A fabric 3 is guided between a drying cylinder 12 and a deflection roller 2, with the web stabilizer 1 being arranged to create a negative pressure in the pocket space 4 formed between the deflection roller 2 and the first fabric 3. The fibrous web is guided between the drying cylinder 12 and the first fabric 3, with the web stabilizer 1 enabling reliable transfer from the drying cylinder 12 to the first fabric 3.

[0028] Fig. 3 shows the web stabilizer 1 according to the invention in a first operating state. The web stabilizer 1 allows the formation of a negative pressure in the pocket space 4 formed between the deflection roller 2 and the clothing 3. The web stabilizer comprises a seal for sealing an end face of the pocket space 4 and in particular for sealing the end face of a gusset 5 formed between the deflection roller 2 and the clothing 3, wherein the seal further comprises the sealing element 6 for sealing the end face against the clothing 3. Fig. 3 shows the first operating state, wherein the fibrous web is guided on the clothing 3 and the end face sealing against the clothing 3 is achieved via the sealing element 6. For this purpose, the sealing element 6 has a contour 7 opposite the clothing 3, which contour is essentially curved for sealing the end face against the clothing 3. Furthermore, Fig.3 shows the further movable sealing element 8 for sealing the end face against the covering 3, which sealing element is shown in a position guided away from the covering 3. Corresponding to the guide 11, the further sealing element 8 can be positioned via the movement means 10, wherein the movement means 10 is connected to the web stabilizer 1. The guide 11 shown in Fig. 3 comprises two elongated holes in the further sealing element 8, wherein the further sealing element 8 is guided in the elongated holes via guide pins and the guide pins are connected to the web stabilizer 1 and in particular to the sealing element 6. In Fig. 3, the further sealing element 8 is positioned corresponding to a first end position of the guide pins in the elongated holes. In particular, the sealing element 6 and the further sealing element 8 are arranged parallel, in particular flush, and offset from one another. Furthermore, the sealing element 6 and the further

[0029] Sealing element 8 is also designed to seal against the deflection roller 2.

[0030] Fig. 4 shows the web stabilizer according to the invention, known from Fig. 3, in a second operating state. In this case, no fibrous web is guided on the fabric 3, and the end-face sealing against the fabric 3 is achieved via the additional sealing element 8, which is guided against the fabric 3 via the movement means 10. The additional sealing element 8 has a further contour 9 opposite the fabric 3, which is essentially formed as a straight line. The additional sealing element 8 is positioned in the elongated holes according to a second end position of the guide pins.

[0031] Advantageously, a sensor allows the detection of the fibrous web on the fabric 3, wherein upon detection of the absence of the fibrous web on the fabric 3, the further sealing element 8 is moved against the fabric.

[0032] Fig. 5 shows the web stabilizer according to the invention with a retracted seal. For this purpose, the sealing element 6 is designed to be movable relative to the web stabilizer 1 for retraction from the gusset 5. Advantageously, the further sealing element 8 is also retracted further from the gusset 5 at the same time as the sealing element 6 is retracted in order to enable optimal accessibility. The present invention offers numerous advantages. The inventor has recognized that the requirements for sealing against the clothing depend greatly on the operating state of the machine. The web stabilizer according to the invention allows the formation of a negative pressure in the pocket space depending on the operating state of the machine, whereby an optimal end-face seal against the clothing can be achieved both for operation with a fibrous web guided on the clothing and for operation without a fibrous web guided on the clothing.Accordingly, the vacuum can be achieved with less effort, or higher vacuums can be achieved with the same effort. In particular, contact between the sealing elements and the covering is avoided or minimized, regardless of the operating condition, which is beneficial for the service life of the covering or the sealing elements.

[0033] Reference symbol

[0034] 1 orbit stabilizer

[0035] 2 deflection roller

[0036] 3 covering

[0037] 4 pocket space

[0038] 5 gussets

[0039] 6 Sealing element

[0040] 7 Contour

[0041] 8 additional sealing element

[0042] 9 further contour

[0043] 10 means of movement

[0044] 11 Guide

[0045] 12 drying cylinders

Claims

Patent claims 1. Web stabilizer (1) for forming a negative pressure in a pocket space (4) formed between a deflection roller (2) and a clothing (3) of a machine for producing a fibrous web, comprising a seal for sealing an end face of the pocket space (4) and in particular for sealing the end face of a gusset (5) formed between the deflection roller (2) and the clothing (3), wherein the seal comprises a sealing element (6) for sealing the end face against the clothing (3), characterized in that the seal comprises a movable, further sealing element (8) for sealing the end face against the clothing (3), wherein the end face sealing against the clothing (3) is provided either via the sealing element (6) or via the further sealing element (8) which is movable against the clothing (3).

2. Web stabilizer (1) according to claim 1, wherein the further sealing element (8) is assigned a movement means (10) for moving the further sealing element (8) against the covering (3), in particular a pneumatic cylinder, a hydraulic cylinder or an actuator.

3. Web stabilizer (1) according to claim 2, wherein the further sealing element (8) is guided in a guide (11) and can be guided against the covering (3) via the movement means (10).

4. The web stabilizer (1) according to claim 3, wherein the guide (11) comprises two elongated holes in the further sealing element (8), the further sealing element (8) is guided in the elongated holes via guide pins, and the guide pins are connected to the web stabilizer and in particular to the sealing element (6).

5. A web stabilizer (1) according to any one of claims 2 to 4, wherein the movement means (10) is connected on the one hand to the web stabilizer (1) and on the other hand to the further sealing element (8).

6. Web stabilizer (1) according to one of claims 1 to 5, wherein the sealing element (6) has a contour (7) opposite the covering (3) and the contour is substantially curved for the end-side sealing against the covering (3).

7. Web stabilizer (1) according to one of claims 1 to 6, wherein the further sealing element (8) has a further contour (9) opposite the covering (3) and the further contour (9) is designed substantially as a straight line for the end-side sealing against the covering (3).

8. Web stabilizer (1) according to one of claims 1 to 7, wherein the sealing element (6) and / or the further sealing element (8) is also designed to seal against the deflection roller (2) and the web stabilizer (1) is designed in particular to suction the deflection roller (2).

9. Web stabilizer (1) according to one of claims 1 to 8, wherein the sealing element (6) and / or the further sealing element (8) is made of a plastic, in particular of polytetrafluoroethylene.

10. Web stabilizer (1) according to one of claims 1 to 9, wherein the sealing element (6) and the further sealing element (8) are arranged parallel, in particular flush, and offset from one another.

11. A track stabilizer (1) according to any one of claims 1 to 10, wherein the sealing element (6) is detachably connected to the track stabilizer (1), in particular via a screw connection.

12. Web stabilizer (1) according to one of claims 1 to 10, wherein the sealing element (6) is designed to be movable relative to the web stabilizer (1) for withdrawal from the gusset (5).

13. Drying group of a machine for producing a fibrous web, comprising a deflection roller (2) which can be vacuumed in particular via the web stabilizer (1), a drying cylinder (12) and a web stabilizer (1) according to one of claims 1 to 12, wherein a clothing (3), in particular a drying wire, is guided around the deflection roller (2) and the drying cylinder (12), wherein the web stabilizer (1) and in particular the seal for sealing the end face is arranged in the pocket space (4) formed between the deflection roller (2) and the clothing (3).

14. Method for forming a negative pressure in a pocket space (4) formed between a deflection roller (2) and a clothing (3) of a machine for producing a fibrous web, wherein the clothing (3) is guided around the deflection roller (2) and a drying cylinder (12) and the pocket space (4) is at least partially suctioned via a web stabilizer (1) according to one of claims 1 to 12, wherein in a first operating state of the Machine, in particular in a state with a fibrous web guided on the clothing (3), the end-face sealing against the clothing (3) is effected via the sealing element (6), and upon a change from the first operating state of the machine to a second operating state of the machine, in particular to a state without a fibrous web guided on the clothing (3), the further sealing element (8) is moved against the clothing (3), wherein in the second operating state of the machine the end-face sealing against the clothing (3) is effected via the further sealing element (8). Method according to claim 14, wherein the machine for producing the fibrous web comprises a sensor for detecting the fibrous web on the clothing (3), and upon detecting an absence of the fibrous web on the clothing (3), the further sealing element (8) is moved against the clothing.

Images