Pressing unit

Abstract

The invention relates to a machine for manufacturing or processing a material web (9), in particular a paper, cardboard, or tissue web, said machine comprising a pressing unit having a press roll (1) and a counter-press roll (8), wherein the press roll (1) is mounted on a pivotable mounting lever (12) and can be moved by means of at least one adjusting unit (14) between an operating position in which the press roll (1) is pressed against the counter-press roll (8) and an inoperative position in which the press roll (1) is not pressed against the counter-press roll (8), characterised in that the pressing unit is a double pressing unit and the press roll (1) mounted on the pivotable mounting lever (12) is arranged as a second press roll (1) in the web running direction of the material web (9).

Description

[0001] The invention relates to a machine for the production or processing of a material web, in particular paper, cardboard or tissue web, with a press unit comprising a press roll and a counter-press roll according to the preamble of claim 1.

[0002] Tissue paper machines, for example, have a press unit formed by a press roll and a counter-press roll designed as a drying cylinder. Often, the press roll is pivotally mounted on a bearing lever relative to the counter-press roll, allowing it to be moved between an operating position, in which the press roll is pressed against the counter-press roll, and an out-of-service position, in which the press roll is not pressed against the counter-press roll, by means of at least one adjusting unit acting on the bearing lever. This adjusting unit is typically a hydraulic cylinder.

[0003] Tissue paper machines of this type are already known from US 2404946A and EP 1 925 723 A1. These machines have a press unit comprising at least one press roll and a counter-press roll, wherein the press roll is mounted on a pivotable bearing lever and can be moved between an operating position, in which the press roll is pressed against the counter-press roll, and an out-of-service position, in which the press roll is not pressed against the counter-press roll, by means of at least one adjusting unit acting on the bearing lever. The known machine includes an adjusting unit with a locking device by means of which the adjusting unit can be mechanically locked in the operating position.

[0004] If the press roller is to be pivoted from the operating position to the out-of-service position, the mechanical locking mechanism created by the locking device can be released again, in order to be re-established at a later time when the press roller has been pivoted back into the operating position.

[0005] From DE 42 16 264 C2, a pressing device is known in which a paper web passes through two press gaps formed by two press rollers and a common counter roller, which the paper web can pass through sequentially together with a felt. Alternatively, instead of using a single felt, two different felts or drying screens are also used.

[0006] The object of the present invention is to create a machine of the type mentioned above in which the aforementioned disadvantages are eliminated, in which, firstly, the exact operating position is maintained without constant force being applied to the adjusting unit, and secondly, an elaborate locking mechanism by means of a locking lever can be dispensed with.

[0007] The problem is solved by the features of claim 1.

[0008] The machine according to the invention for producing or processing a web of material comprises a press unit including at least one press roller and a counter-press roller, wherein the press roller is mounted on a pivotable bearing lever and is movable between an operating position, in which the press roller is pressed against the counter-press roller, and an out-of-service position, in which the press roller is not pressed against the counter-press roller, by means of at least one adjusting unit acting on the bearing lever. The machine according to the invention is characterized in that the press unit is a double press unit and that the press roller mounted on the pivotable bearing lever is arranged as the second press roller in the web direction of the web and can be pressed against a press gap to generate a predetermined pressing pressure.

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

[0010] One embodiment of the invention provides that the operating position comprises several operating positions in which each of the press rollers and the counter-press roller are pressed against each other with varying degrees of force, wherein the locking device is designed such that the adjusting unit is mechanically adjustable in each of the different operating positions. It is further provided that the first press roller is also arranged to be pivotable.

[0011] The second press roller is designed as a shoe press roller. Because the press roller incorporates a pressure shoe, it does not require internal support sources to close the nip between the pressure shoe and the counter roller. According to the invention, the nip is closed by the external lever system, i.e., the pressing pressure is applied. The line force of the press nip is also generated by the external lever system, so that the press roller is comparable to a conventional press roller or suction press roller.

[0012] However, it can be provided that the pressure shoe is mounted on a support element or a plurality of support elements. If several individually mounted support elements are provided, these can have different hardnesses, particularly at their two edges, in edge zones to improve the contact pressure of the pressure shoe against the counter-pressure roller. In this case, the counter-pressure roller is preferably a Yankee cylinder. The edge zones each have a width of less than 500 mm, preferably less than 300 mm.

[0013] The invention offers the advantage that the pressing system and the movement system of the shoe press are combined in a single system. No safety control or monitoring of the linear force is required. Instead, a shoe press roller controlled according to the invention can be treated like a conventional press roller, with press levers actuated by actuators acting externally on the shoe press roller. The maximum linear load is ensured by the oil pressure in the actuators or hydraulic cylinders. Furthermore, no hydraulic zone control of the pressure shoe is required; a single lubrication unit is sufficient for the press sleeve enclosing the pressure shoe. The simple design of the shoe press roller without an internal adjustment mechanism results in cost savings.

[0014] The distance between the shoe press roller and the counter roller is freely adjustable, whereas with internal support sources, the stroke is limited by the press shell to a distance of approximately 20 to 30 mm. This small distance can lead to damage to the leather covering if the counter roller is hot.

[0015] According to the invention, less deformation of the press shell and the press sleeve of the shoe press roller is enabled, whereas the stroke of an active internal pressure system according to the prior art causes the shell of the shoe press roller to bulge or deform.

[0016] A further advantage of the pivotable shoe press roller according to the invention is that no change in nip force occurs when the diameter of the counter roller, for example the Yankee cylinder, changes. Only one force is applied by the adjustment mechanism, while the position of the shoe press roller is variable and adapts to that of the counter roller.

[0017] According to a particularly advantageous embodiment, it is provided that the dewatering process can be optimized by rotating the press roller in or against the direction of machine travel.

[0018] The shoe press roller has a rotatably mounted pressure shoe or a pressure shoe arranged in a flexible connection.

[0019] It is also advantageous if the shoe press roller, particularly in the edge areas, has a pressure shoe divided into a number of individually mounted or controllable zones, or zones with different degrees of hardness. This allows the contour of the counter press roller, especially a Yankee cylinder, to be followed precisely.

[0020] In another advantageous embodiment, it is provided that the shoe press roller has at least one yoke along its length for supporting the pressure shoe.

[0021] Preferably, the press shoe is mounted within the press roller on at least one soft, elastically compliant support element, which in turn rests on at least one yoke. The pressing pressure between the counter-press roller and the press shoe can be controlled by means of the bearing lever. Because the press roller is mounted on a soft, elastically compliant, and flexible support element, the press shoe can be pressed against the contour of the counter-roller, for example, a Yankee cylinder, with the same contact pressure across its entire width to close the nip between the press shoe and the counter-roller. Due to the compliant and soft structure of the support element, the contact pressure of the press shoe is continuously adjusted and maintained.

[0022] This means that, according to the invention, deformations in the contour of the counter roll, for example the Yankee cylinder, which arise, for instance, from temperature fluctuations during operation, are compensated for by the elasticity of the support element. Thus, if the outer surface of the counter roll assumes a convex or concave shape during operation, this change in shape is compensated for by the correspondingly deforming support element in such a way that the press shoe always bears against the counter roll in the press nip with the same contact pressure. Preferably, the contact pressure is regulated. The moisture content and / or temperature of the material web can preferably be selected as the control variable for determining the contact pressure.

[0023] According to the invention, instead of a single support element, a plurality of adjacent support elements can be provided, which are preferably connected to one another. These can have different hardnesses, particularly at the two edges, in edge zones to improve the contact pressure of the press shoe against the counter-press roller. In this case, the counter-press roller 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 that a dewatering element, in particular a suction box or a suction turning roller, is arranged upstream of the second press roller in the web direction of the material web.

[0025] Another advantageous embodiment provides that the second press roller has a diameter of at least 750 mm.

[0026] It is also advantageous if, in the web direction of the material web, a first press roller designed as a suction press roller is arranged in front of the second press roller in the press unit comprising the counter press roller.

[0027] It is particularly advantageous to provide a drying cylinder, especially a Yankee drying cylinder, or a smoothing cylinder as a counter-pressure roller.

[0028] The invention is explained in more detail below using exemplary embodiments with reference to the following drawings. These show: Fig. 1 schematic representation of a shoe press roller that can be used according to the invention, Fig. 2 a shoe press roller that can be adjusted to a counter roller by means of a bearing lever and Fig. 3 A detailed view of a pressure shoe equipped with elements for equalizing the pressure force in a shoe press roller.

[0029] A shoe press roller 1 ( Fig. 1 The device, intended for use in the press section of a paper machine or other machine for processing a material web, comprises a pressure shoe 2 with a base 3. The pressure shoe 2 is rotatable relative to the base via a pivot point 4. Alternatively, instead of a rotatable arrangement of the pressure shoe 2, a flexible connection to the base can also be established, for example, by means of a specifically weakened material or a plastic. Furthermore, a passive, i.e., not actively controlled, element 5 is provided for equalizing the pressure force transverse to the machine direction. An element 6 forms a connection to at least one yoke arranged in the shoe press roller 1, which serves to increase the stability of the shoe press roller. An arrow 7 indicates the adjustability of the shoe press roller 1 via the roller bearing in the machine direction.

[0030] The shoe press roller 1 ( Fig. 2 During operation, the shoe press roller 1 rests against a counter roller 8. A web of material 9, in particular a paper web, is guided between the shoe press roller 1 and the counter press roller 8. From a deflection roller 10 and over the shoe press roller 1, the web of material 9 is guided, for example, over a first felt or fabric layer (not shown here), while before this point, i.e., over a first press roller 11 resting against the counter cylinder 8, and up to the deflection roller 10, the web of material 9 is guided over a second felt or fabric layer (also not shown).

[0031] The shoe press roller 1 thus forms the second press roller, which rests against the counter press roller 8. The shoe press roller 1 is rotatably mounted on, for example, an L-shaped bearing lever 12 about its axis of rotation 13. The bearing lever 12 is mounted about its axis of rotation 13 on a machine support (not shown). By means of an adjusting unit 14, designed as a hydraulic cylinder and acting on the bearing lever 12, the shoe press roller 1 can be moved between an operating position, in which it is pressed against the counter press roller 8, for example, a Yankee drying cylinder, and a non-operating position, in which the shoe press roller 1 is not pressed against the counter press roller 8. In the operating state, a press nip is formed between the shoe press roller 1 and the counter roller 8, through which the material web 9 is guided.The press roller 11 can also be equipped in a similar manner with an adjustment mechanism for setting the press nip between it and the counter roller 8.

[0032] A pressure shoe 2 ( Fig. 3 In one embodiment, a shoe press roller 1 is equipped with two rotatable elements 15, 16 mounted inside the shoe press roller 1 to even out the pressing force. The number of elements 15, 16 can be selected differently. Depending on the direction of the force, the elements 15, 16 have different degrees of hardness. This allows for the creation of various counterforces or degrees of softness. By segmenting these elements 15, 16, more or less Niplast, and thus Niplast, can be selectively applied to the nip formed between the pressure shoe 2 (e.g., made from a block of polyurethane) and the shoe press roller 1. This is particularly important in the edge regions of the counter press roller 8 and the material web 9. Hydraulic rams can also be used inside the shoe press roller 1 to apply a uniform pressing force to the counter press roller 8.Preferably, the hydraulic cylinders can also be mounted at a distance of 10 cm from the edge of the shoe press roller 1. Alternatively, a plurality of hydraulic cylinders can be provided as support elements, which, for example, can be spaced approximately 10 cm apart. The pressing force can be applied continuously. A large number of pressure elements are not required.

[0033] According to the invention, the press roller, in particular the shoe press roller 1, has, for example, a diameter of 770 mm. A diameter of 1100 mm can be used if sufficient installation space is available or for wider machines. The shoe press roller 1 can be installed in a conventional shoe press configuration, i.e., with an upstream dewatering element such as a suction box or a suction reversing roller.

[0034] According to the invention, the shoe press roller 1 is used as a second press in a Fig. 2Due to its compact design, the double press unit shown is used as a swiveling unit with a diameter of 770 mm using a swiveling or bearing lever 13.

[0035] According to the invention, the material web 9 is applied to the counter-pressing roller 8 by a first press roller 11, preferably designed as a suction press roller, and is heated by the counter-pressing roller 8, designed as a drying cylinder, before reaching the second nip formed with the shoe press roller 1, in order to achieve maximum dryness levels.

Claims

1. Machine for producing or processing a material web (9), in particular a paper, cardboard or tissue web, with a pressing unit comprising a press roll (1) and a counter-press roll (8), wherein the press roll (1) is mounted on a pivotable mounting lever (12) and, by means of at least one adjustment unit (14), is movable between an operative position, in which the press roll (1) is pressed against the counter-press roll (8), and a non-operative position, in which the press roll (1) is not pressed against the counter-press roll (8), and wherein the pressing unit is a double pressing unit, and the press roll (1) mounted on the pivotable mounting lever (12) is arranged as a second press roll (1) in the running direction of the material web (9) and can be pressed on in order to generate a predetermined pressing pressure in a press nip, characterized in that the second press roll (1) is designed as a shoe press roll, and in that the shoe press roll (1) has a rotatably mounted pressure shoe (2) or a pressure shoe (2) arranged in a flexible connection, wherein the flexible connection is designed as a mounting on a soft, elastically yielding support element.

2. Machine according to Claim 1, characterized in that the shoe press roll (1), in particular in the edge regions, has a pressure shoe (2) divided into a plurality of individually mounted or controllable zones or has zones with different degrees of hardness.

3. Machine according to either of Claims 1 and 2, characterized in that the shoe press roll (1) has, along its length, at least one yoke for mounting the pressure shoe (2).

4. Machine according to any one of Claims 1 to 3, characterized in that the second press roll (1) is preceded by a dewatering element, in particular a suction box or a suction turning roll, in the running direction of the material web (9).

5. Machine according any to one of Claims 1 to 4, characterized in that the second press roll (1) has a diameter of at least 750 mm.

6. Machine according to any one of Claims 1 to 5, characterized in that the second press roll (1) is rotatable in the machine running direction or rotatable counter to the running direction of the machine.

7. Machine according to any one of Claims 1 to 6, characterized in that, in the running direction of the material web (9), a first press roll (11) designed as a suction pressure roll is arranged upstream of the second press roll (1) of the pressing unit comprising the counter-press roll (8).

8. Machine according to any one of Claims 1 to 7, characterized in that the counter-press roll (8) is a drying cylinder, in particular a Yankee drying cylinder (2), or a smoothing cylinder.

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