The invention relates to an apparatus for forming an extended nip between a mating roll and a shoe roll for treating a material web, in particular a paper web, a board web, a tissue web, or any other fibrous web.
Apparatus of this type are used in particular in press sections and calendars.
DE 30 30 233 C3 discloses a wet press for dewatering fibrous webs, in which an elongated press zone is applied so as to substantially increase dewatering as compared with other press rolls. On account of a concave shape of the sliding face of the sliding shoe, an elongated press nip through which the fibrous web passes is formed between a mating roll and a rotating belt on which a sliding shoe bears from the inside. The rotating belt is held in a substantially roll-like shape by annular discs which are fastened to the end sides of the belt. The sliding shoe is fastened to a shoe base which is connected to a stationary yoke by way of a pressure cushion from an elastic material, for example plastics or rubber, and in relation to said yoke is guided in the direction of pressure by pins and transversely thereto is held in a form-fitting manner. Metal strips serve for fastening the pressure cushion to the shoe base and to the yoke.
The space which is enclosed by the pressure cushion is loadable via lines by a fluid, such that it is possible for the contact pressure of the sliding shoe on the mating roll to be varied. The pressure cushion here is disposed such that the resulting force applied by the pressure cushion on the sliding shoe in the running direction of the roll circumference runs through the second half of the formed press nip. As a result, a slow increase in pressure which thereafter at the end of the press zone rapidly decreases is caused, being advantageous for a dewatering operation. In order to be able to adjust different contact pressures across the roll width, the pressure cushion may be axially subdivided into zones. It is disadvantageous that the pressure cushion from an elastic material, for example plastics or rubber, is liable to wear. The cost advantages of pressure cushions as compared to more complex cylinder-type loading systems are therefore often lost on account of comparatively short maintenance intervals.
U.S. Pat. No. 4,713,147 discloses a wet press having an elongated press nip, in which two separate pressure cushions are provided for adjusting the line load along the length of the press zone of the press nip. Thereby, the shape of the pressure curve is better adjustable. However, the disadvantages mentioned above apply in a corresponding manner.
It is therefore an object of the invention to provide an apparatus for forming an extended nip according to the preamble of Claim 1, in which the press shoe by way of a fluid-loadable pressure cushion as a contact pressure unit is pressable against the mating roll and the pressure cushion here operates with low wear.
This object is achieved by the features of Claim 1.
By this means, an apparatus for forming an extended nip is provided, in which all frictional effects between a male form portion of the press shoe and the pressure cushion, on the one hand, and the groove-type chamber and the pressure cushion, on the other hand, are avoided. While avoiding stick-and-slip effects, the pressure cushion can be unfolded by the lateral guide of a rollable wall from a flat first profile to a higher second profile, by which a lifting movement of the press shoe is performed. The lifting movement enables displacement of the press shoe in relation to the roll shell and adjustment of a pressure in the extended nip. The pressure cushion is thus subject to substantially lower wear.
According to the invention the loading of the pressure cushion with fluid is a hind of inflating fluid loading, in which the rollable wall always forms a rolling fold which is maintained in all operational states. The rolling behaviour of the rollable wall enables guiding of a male form portion of the shoe, which extends in an axial manner along a shoe length which typically runs in a transverse manner to the machine direction (MD).
According to preferred exemplary embodiments, the pressure cushion is made from a flexible material which also configures the rollable wall having a rolling fold. Here, the male form portion of the press shoe between two axially extending rolling folds projects into the pressure cushion while sinking the latter.
It is furthermore advantageous that the pressure cushion is formed by a fluid-loadable flexible tube, the two material layers of said tube, which in the cross section are disposed on top of one another, are placed in a U-shape in the groove-type chamber in such a manner that the tube folds of the leg ends of the tube which is place in a U-shaped manner form the rollable wall. The rollable wall is then configured so as to be integral with the pressure cushion, as a result which a pressure cushion which can be readily and rapidly fitted is moreover achieved. Alternatively, a forming part having a rollable wall which is clamped at the end sides may be provided.
Furthermore, a several of pressure cushions can be provided longitudinally across shoe width in the machine direction, having assigned one male form portion of the press shoe, respectively. Setting of the line load along the press zone length of the extended nip is then variable.
In order for different contact pressures to be able to be set across the shoe length, that is to say across the roll width in a transverse direction to the machine direction, the pressure cushion may be axially subdivided into zones. Alternatively or additionally, the male form portion of the press shoe can plunge into the pressure cushion or pressure cushions by way of variably sized contact areas. Thus, peripheral loading or load relief of the press shoe is adjustable. Moreover, additional cylinder-type loading installations, by way of which the line load profile along the press zone in the extended nip may be varied, can also be provided.
Further refinements of the invention can be gathered from the following description and the dependent claims.
The invention will be explained in more detail below by using the exemplary embodiments illustrated in the appended figures, in which:
As shown in
The shoe roll 3 comprises a carrier 4 and a flexible roll shell 5 which is rotatable about the carrier 4. The carrier 4 is preferably configured as a stationary yoke. The roll shell 5 in the region of the extended nip 1 is supported on a head face 7 of a press shoe 6 which is guided on the carrier 4. The press shoe 6 for generating a pressure by way of at least one fluid-loadable pressure chamber, presently, according to the first exemplary embodiment, the pressure chambers 8, 9, is movably supported on the carrier 4.
The pressure chamber 8, 9 is configured as a pressure cushion 10 on which the press shoe 6 by way of the rear side is supported in a planar manner, wherein the pressure cushion 10 is placed in a groove-type chamber 11.
The press shoe 6 on the rear side has at least one male form portion 12 or a base, respectively, which for performing lifting movements projects into at least one pressure cushion 10 which can be sunk. To this end, the pressure cushion 10 is supported in a guiding manner by way of a pressure-cushion side wall, which forms a rollable wall 13, on the groove-type chamber 11. This can be achieved by the pressure cushion 10 being made from a flexible material.
The rollable wall 13 forms a rolling fold 14 between the male form portion 12 of the press shoe 6 and an inner side wall 15 of the grove-type chamber 11. The rolling behaviour of the rollable wall 13 determines a lifting length in the lifting direction. Preferably, a clear height H of the groove-type chamber 11 should be at least half of the lifting movement of the press shoe 6 in the direction of pressure X, as is clarified in
A spacing Y between the male form portion 12 of the press shoe 6 and the inner side wall 15 of the groove-type chamber 11 is selected such that the rollable wall 13 during displacement of the male form portion 12 in the lifting direction is pressed against the inner side wall 15 of the groove-type chamber 11.
A substantial advantage of the pressure cushion 10 also lies in that the compression surface of the pressure cushion 10 which acts on the male form portion 12 is independent of the lifting movements, as is shown in
As a pressure cushion 10, a fluid-loadable flexible tube 16 is preferably placed in the axially extending groove-type chamber 11. The two material layers 17, 18, of the tube 16, which in the cross section are disposed on top of one another, are placed in a U-shape in the groove-type chamber 11 in such a manner that the tube folds of the leg ends of the tube which is placed in a U-shaped manner form the rollable wall 13. The male form portion 12, which is engaged for lifting with the pressure cushion 10, while performing lifting movements is enclosed by the tube 16 in a U-shaped cross-sectional manner.
The tube 16 preferably consists of a fibre-reinforced plastic material or of a fibre-reinforced rubber compound. The rollable wall 13 is then configured so as to be integral with the tube 16.
The press shoe 6 is brought into contact with the mating roll 2 or a mating element and pressed there against by way of at least one pressure, and when two pressure cushions 10 are provided according to
As an alternative to a tube, the pressure cushion 10 can be formed by a flexible shaped piece 19, which at the end side is clamped to fixing points 20, as is shown in
According to
As is shown in the described
As is shown in
As is shown in
As is finally shown in
The male form portion 12 having a comparatively small bearing face 26 can be assigned a separate force component F1, F2 for increasing a localized press force. The point of attack of these additional force components F1, F2 preferably lies between the exemplary two male form portions 12, as is clarified in
As is shown in
In the case of all exemplary embodiments a cloth 28 can be placed as wear protection between the head face 7 of the press shoe 6 and the roll shell 5, as is illustrated in an exemplary manner in
The apparatus described above may find use as a wet press or a calender.
Number | Date | Country | Kind |
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13002777 | May 2013 | EP | regional |
Filing Document | Filing Date | Country | Kind |
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PCT/EP2014/001424 | 5/27/2014 | WO | 00 |
Publishing Document | Publishing Date | Country | Kind |
---|---|---|---|
WO2014/191101 | 12/4/2014 | WO | A |
Number | Name | Date | Kind |
---|---|---|---|
4713147 | Saarinen | Dec 1987 | A |
6174272 | Savia | Jan 2001 | B1 |
7527708 | Gustavsson | May 2009 | B2 |
7722744 | Mueller | May 2010 | B2 |
Number | Date | Country |
---|---|---|
3030233 | Feb 1982 | DE |
1505204 | Feb 2005 | EP |
WO2005042834 | May 2005 | WO |
Entry |
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English Translation of the International Preliminary Report on Patentability corresponding to PCT/EP2014/001424 dated Dec. 1, 2015. |
International Search Report corresponding to PCT/EP2014/001424 dated Jun. 16, 2014. |
European Search Report corresponding to EP13002777 dated Jul. 13, 2015. |
Number | Date | Country | |
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20160108579 A1 | Apr 2016 | US |