Pressing unit

Abstract

A machine for producing or processing a material web (9), in particular a paper, cardboard or tissue web, having a pressing unit comprising a pressing roller (1) and a counter-pressing roller (8), wherein the pressing roller (1) is supported on a pivotable support arm (12) and can be moved by at least one adjustment unit (14) between an operating position and a rest position, in which the pressing roller (1) presses on the counter-pressing roller (8) and in which the pressing roller (1) does not press on the counter-pressing roller (8), characterised in that the pressing unit is a double pressing unit and the pressing roller (1) supported on the pivotable support arm (12) is arranged as the second pressing roller (1) in the web travel direction of the material web (9).

Description

Technical Field

[0001] The invention relates to a machine for producing or processing a material web, in particular a paper, cardboard or tissue web, with a pressing unit comprising a pressing roll and a counter-pressing roll. Background Art

[0002] A tissue machine, for example, has a press unit consisting of a press roller and a counter-press roller designed as a drying cylinder, wherein the press roller is usually mounted on a support arm so as to be pivotable relative to the counter-press roller, so that the press roller can be moved by at least one adjusting unit acting on the support arm between an operating position, in which the press roller presses against the counter-press roller, and a rest position, in which the press roller does not press against the counter-press roller. The adjusting unit is usually designed as a hydraulic cylinder.

[0003] EP 1 925 723 A1 discloses a tissue machine having a press unit comprising at least one press roller and a counter-press roller, wherein the press roller is mounted on a pivotable support arm and can be moved by at least one adjusting unit acting on the support arm between an operating position, in which the press roller presses against the counter-press roller, and a rest position, in which the press roller does not press against the counter-press roller. The known machine includes an adjusting unit with a locking device, which can be mechanically locked in the operating position.

[0004] If the press roll is to be pivoted from the operating position into the rest position, the mechanical locking established by the locking device can be released again in order to reestablish the locking at a later point in time when the press roll is pivoted back into the operating position.

[0005] Document DE 42 16 264 C2 discloses a press device in which the paper web passes through two press nips formed by two press rolls and a common counterroll, through which the paper web and the felt can pass successively. Alternatively, two different felts or drying screens can be used instead of a single felt. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to realize a machine of the type mentioned at the outset in which the aforementioned disadvantages are overcome, wherein on the one hand the precise operating position is maintained without permanent and stable force loading of the adjustment unit, wherein at the same time the locking mechanism consumed by the locking arm can be omitted.

[0007] This object is achieved by the features of claim 1 .

[0008] The machine according to the invention for producing or processing a material web comprises a press unit comprising at least one press roll and a counter-press roll, wherein the press roll is mounted on a pivotable support arm and can be moved by at least one adjustment unit acting on the support arm between an operating position, in which the press roll presses against the counter-press roll, and a rest position, in which the press roll does not press against the counter-press roll. The machine according to the invention is characterized in that the press unit is a double press unit and the press roll mounted on the pivotable support arm is arranged as the second press roll in the web travel direction of the material web and can be pressed together to generate a predetermined pressing pressure in the press nip.

[0009] Advantageous embodiments of the invention are described in the dependent claims.

[0010] One embodiment of the invention provides that the operating position comprises a plurality of operating states in which each press roll and the counter-press roll press against each other to different degrees, wherein the locking device is designed so that the adjustment unit can be mechanically adjusted in each of the different operating states. It is provided that the first press roll is also arranged so as to be pivotable.

[0011] Preferably, the second press roll is designed as a shoe press roll. The press roll comprises a pressure shoe, which eliminates the need for an internal support source in order to close the nip between the pressure shoe and the counter roll. According to the invention, the nip is closed, i.e., the pressing pressure is applied, by an external lever system. The linear force of the press nip is also generated by the external lever system, making the press roll similar to a conventional press roll or a suction press roll.

[0012] However, it can be provided that the press shoe is supported on one or more support elements. If a plurality of individually supported support elements are provided, they can have different hardnesses, particularly at the two edges in the edge region, to improve the pressure against the counter-press roll. In this case, the counter-press roll is preferably a Yankee cylinder. The edge regions each have a width of less than 500 mm, preferably less than 300 mm for the press shoe.

[0013] The advantage achieved according to the invention is that the pressing system and the movement system of the shoe press are unified into one system. No safety control devices or monitoring of the line forces are required. On the contrary, the shoe press roll controlled according to the invention can be handled like a conventional press roll, wherein a pressing arm operated by an actuator acts on the shoe press roll from the outside; the maximum line load is ensured by the oil pressure in the actuator or hydraulic cylinder. There is also no need for hydraulic zone control of the press shoe; instead, a single lubrication device for the press sleeve (sleeve) surrounding the press shoe is sufficient. Costs are saved due to the simple design of the shoe press roll and the lack of internal adjustment mechanisms.

[0014] The distance between the shoe press roll and the counter roll can be set arbitrarily, while in the case of an internal support source, the stroke is limited to a distance of about 20 to 30 mm by the press hood. This smaller distance can lead to damage to the clothing when the counter roll is hot.

[0015] According to the invention, a smaller deformation of the press sleeve and the press sleeve of the shoe press roll is achieved, whereas the press sleeve of the shoe press roll bulges or deforms due to the stroke of the active internal hold-down system according to the prior art.

[0016] A further advantage of the pivotable shoe press roll according to the invention is that the nip force does not change when the diameter of the counter roll, for example the Yankee cylinder, changes. Only one force needs to be applied by the adjustment mechanism, while the position of the shoe press roll is variable and adapted to the position of the counter roll.

[0017] According to a particularly advantageous embodiment, the dewatering process can be optimized by rotating the press rolls in the machine direction or counter to the machine direction.

[0018] According to an advantageous embodiment, the shoe press roll has a rotatably mounted press shoe or a press shoe arranged in a flexible connection.

[0019] It is also advantageous if the shoe press roll has a press shoe divided into several individually supported or controllable areas or areas of different hardness, especially in the edge area. This allows for exact tracking or adaptation to the contour of the mating press roll, especially the Yankee cylinder.

[0020] In a further advantageous embodiment, it is provided that the shoe press roll has at least one yoke over its length for supporting the press shoe.

[0021] The press shoe is preferably supported within the shoe press roll on at least one soft, elastically yielding support element, which in turn rests on at least one yoke. The pressing pressure between the counter-press roll and the press shoe can be controlled via a support lever. The support of the press roll on the soft, elastically yielding, and flexible support element allows the press shoe to press against the counter-roll, such as the profile of a Yankee cylinder, with uniform pressure across the entire width in order to close the nip between the press shoe and counter-roll. Due to the yielding and soft design of the support element, the pressure of the press shoe is continuously tracked and adapted.

[0022] This means that deformations in the counterroll, such as the Yankee cylinder, caused by temperature effects during operation, for example, are compensated by the elasticity of the support element. Thus, if the outer surface of the counterroll assumes a convex or concave shape during operation, this shape change is compensated by the correspondingly deformed support element, so that the press shoe always rests on the counterroll with the same pressure force in the press nip. The pressing pressure is preferably regulated. The moisture content and / or temperature of the material web can preferably be selected as the control variable for determining the pressing pressure.

[0023] According to the invention, instead of a single support element, a plurality of support elements, preferably connected to one another and arranged side by side, can be provided. The individually supported support elements can have different hardnesses, particularly at the two edges in the edge region, in order to improve the pressing of the press shoe against the mating press roll. In this case, the mating press roll is preferably a Yankee cylinder. The edge regions each have a width of less than 500 mm, preferably less than 300 mm.

[0024] It is also advantageous if a dewatering element, in particular a suction box or a suction reversing roller, is arranged upstream of the second press roller in the web running direction of the material web.

[0025] A further advantageous embodiment provides that the second press roll has a diameter of at least 750 mm.

[0026] It is advantageous if, in a press unit comprising a counter-press roll, a first press roll configured as a suction press roll is arranged upstream of a second press roll in the web running direction of the material web.

[0027] It is particularly advantageous if a drying cylinder, in particular a Yankee drying cylinder or a smoothing cylinder, is provided as the counter-press roll. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The present invention is further described below with reference to the accompanying drawings and examples.

[0029] Figure 1 shows a schematic diagram of a shoe press roll that can be used according to the invention,

[0030] Figure 2 Shows a shoe press roll that can be adjusted to the mating roll via a support arm,

[0031] Figure 3 A detailed view of a press shoe provided with elements for equalizing the pressure in a shoe press roll is shown. DETAILED DESCRIPTION

[0032] Shoe press roll 1 (for use in the press section of a papermaking machine or other machine for processing a material web) Figure 1 ) comprises a press shoe 2 with a substructure 3. The press shoe 2 can be rotated relative to the substructure via a pivot point 4. As an alternative to a rotatable arrangement of the press shoe 2, a flexible connection to the substructure can be established, for example by means of a specially weakened material or plastic. Furthermore, a passive, i.e., non-actively controlled, element 5 is provided for homogenizing the pressure transversely to the machine direction. Element 6 is a connection to at least one yoke arranged in the shoe press roll 1, which serves to increase the stability of the shoe press roll. Arrow 7 indicates the possibility of adjusting the shoe press roll 1 in the machine direction via the rolling bearing.

[0033] Shoe press roll 1( Figure 2 ) during operation, rests against the counter-roll 8. A material web 9, in particular a paper web, is guided between the shoe press roll 1 and the counter-press roll 8. Starting from the deflecting roll 10 and on the shoe press roll 1, the material web 9 is guided, for example, on a first felt or clothing section (not shown here), whereas before this, on a first press roll 11 resting against the counter-roll 8, and up to the deflecting roll 10, the material web 9 is guided on a second felt or clothing section (also not shown here).

[0034] The shoe press roll 1 thus forms a second press roll, which rests against the counter-press roll 8. The shoe press roll 1 is rotatably supported about its rotation axis 13 on an L-shaped support arm 12, for example. The support arm 12 is supported by its rotation axis 13 on a machine frame (not shown). An adjustment unit 14, designed as a hydraulic cylinder and acting on the support arm 12, allows the shoe press roll 1 to be moved between an operating position, in which the shoe press roll presses against the counter-press roll 8, for example, a Yankee dryer, and a rest position, in which the shoe press roll 1 does not press against the counter-press roll 8. In the operating position, a press nip is formed between the shoe press roll 1 and the counter-press roll 8, through which the material web 9 is guided. The press roll 11 can also be equipped with an adjustment mechanism in a similar manner for adjusting the press nip between it and the counter-press roll 8.

[0035] According to one embodiment, the press shoe 2 ( Figure 3 ) is equipped with two rotatable elements 15, 16 supported inside the shoe press roll 1 for uniforming the pressing pressure, wherein the number of elements 15, 16 can be selected to be different. Depending on the direction of the force, the elements 15, 16 have different hardnesses. This allows different reaction forces or softness to be achieved. By partitioning the elements 15, 16, more or less nip load and thus the nip load can be applied in a targeted manner to the nip formed between the press shoe 2, which is made of, for example, a polyurethane block, and the shoe press roll 1. This is particularly important in the edge area of ​​the mating press roll 8 and the material web 9. In order to apply a uniform pressing pressure to the mating press roll 8, a hydraulic punch can also be used inside the shoe press roll 1. Preferably, the hydraulic cylinder can also be installed at a distance of 10 cm from the edge of the shoe press roll 1. It is also possible to provide multiple hydraulic cylinders as supports, which can, for example, be at a distance of about 10 cm from each other. The pressing pressure can be applied continuously. Multiple pressing elements can be omitted.

[0036] According to the invention, the press roll, in particular the shoe press roll 1, has a diameter of, for example, 770 mm. A diameter of 1100 mm can be used if there is sufficient installation space or for wider machines. The shoe press roll 1 can be installed as a conventional shoe press, i.e. with an upstream dewatering element, such as a suction box or a suction reversing roll.

[0037] The shoe press roll 1 according to the present invention is Figure 2 The double pressing unit shown is used as the second press because of its compact design with a diameter of 770 mm and can be used as a pivotable unit using a pivoting arm or support arm 13 .

[0038] According to the invention, the material web 9 is applied to the counter-pressing roll 8 by a first press roll 11, which is preferably designed as a suction press roll, and is heated by the counter-pressing roll 8, which is designed as a drying cylinder, before reaching the second press zone formed with the shoe press roll 1 to achieve a maximum dry weight content.

Claims

1. A machine for producing or processing a material web (9) with a pressing unit comprising a pressing roll (1) and a counter-pressing roll (8), wherein: The press roll (1) is supported on a pivotable support arm (12) and can be moved by at least one adjustment unit (14) between an operating position, in which the press roll (1) presses against the counter-press roll (8), and a rest position, in which the press roll (1) does not press against the counter-press roll (8). It is characterized in that The pressing unit is a double pressing unit and a pressing roller (1) supported on a pivotable supporting arm (12) is arranged as a second pressing roller in the web travel direction of the material web (9) and can be pressed in order to generate a predetermined pressing pressure in the pressing gap, wherein the second pressing roller is configured as a shoe-type pressing roller having a rotatably supported pressing shoe (2) or a pressing shoe (2) arranged in a flexible connection.

2. The machine according to claim 1, It is characterized in that The shoe press roll has a press shoe (2) in the edge region which is divided into a plurality of individually supported or controllable regions or regions of different hardness.

3. A machine according to claim 1 or 2, It is characterized in that The shoe press roll has at least one yoke along its length for supporting the press shoe (2).

4. The machine according to claim 1 or 2, It is characterized in that A dewatering element is arranged in front of the second press roller in the web running direction of the material web (9).

5. The machine according to claim 1 or 2, It is characterized in that The second press roll has a diameter of at least 750 mm.

6. The machine according to claim 1 or 2, It is characterized in that The second press roll can rotate in the machine direction or counter to the machine direction.

7. The machine according to claim 1 or 2, It is characterized in that For the press unit including the mating press roll (8), a first press roll (11) configured as a suction press roll is arranged in front of the second press roll in the web running direction of the material web (9).

8. The machine according to claim 1 or 2, It is characterized in that The mating pressing roller (8) is a drying cylinder or a smoothing cylinder.

9. The machine according to claim 1, characterized in that The material web (9) is a paper web, a cardboard web or a tissue web.

10. The machine according to claim 4, characterized in that The dewatering element is a suction box or a suction reversing roller.

11. The machine according to claim 8, characterized in that The drying cylinder is a Yankee drying cylinder.

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