Paper making and fiber liberation – Processes and products – Running or indefinite length work forming and/or treating...
Reexamination Certificate
1997-12-12
2001-04-03
Hastings, Karen M. (Department: 1731)
Paper making and fiber liberation
Processes and products
Running or indefinite length work forming and/or treating...
C162S360200, C162S360300, C162S358300
Reexamination Certificate
active
06210530
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATION
The present application claims priority under 35 U.S.C. § 119 of German Patent Application No. 196 52 018.5 filed Dec. 13, 1996, the disclosure of which is expressly incorporated by reference herein in its entirety.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a press section of a machine for producing a fibrous web, e.g., a paper or cardboard web, having at least two nips extended in length in a web travel direction. Each of the at least two nips is formed between a revolving flexible press belt of a shoe press unit and a counterpart face. The flexible press belt can be pressed against the counterpart face by at least one press shoe associated with the respective shoe press unit. The respective nip length may be determined at least substantially by the press shoe length, measured in the web travel direction, of the associated shoe press unit.
2. Discussion of Background Information
The advantages of extended nip presses known in the art include, inter alia, that the nip is no longer substantially linear but instead is two-dimensional. In this manner, the still-wet fibrous web is exposed to pressing pressure over a longer distance and, thus, is more intensively dewatered. Further, the onset of pressure in the nip is no longer sudden. Instead, the pressure can be brought continuously, e.g., from a low value to a high value, thus, avoiding a risk that the fibrous web will become crumpled in the nip.
In previous conventional press sections similar in general to the type described above, the shoe press units associated with the various nips have identical press shoes, or press shoes of equal length. Thus, the press section includes nips of the same length.
SUMMARY OF THE INVENTION
The present invention provides a press section of the type generally described above, while retaining as simple and compact a structure of the shoe press units as possible to ensure optimal handling of the fibrous web.
In accordance with the present invention, nips of various lengths may be formed. In forming the various lengths of nips, at least some of the shoe press units have different press shoe lengths.
In another embodiment of the present invention, the shoe press unit associated with the first nip in the web travel direction has a greater press shoe length than the shoe press unit associated with the last nip in the web travel direction.
The shoe press unit associated with the first nip in the web travel direction may advantageously have a press shoe length approximately two to five times as long as the shoe press unit associated with the last nip in the web travel direction.
In an alternative embodiment of the present invention, the shoe press unit associated with the first nip in the web travel direction may have a press shoe length less than the shoe press unit associated with the last nip in the web travel direction.
In a particularly advantageous embodiment of the present invention, three shoe press units may be provided. The shoe press unit associated with the first nip in the web travel direction may have a greater press shoe length than a middle shoe press unit, and the press shoe length of the middle shoe press unit may be greater than a press shoe length of a shoe press unit associated with the last nip in the web travel direction.
It may be particularly advantageous, in accordance with the present invention, to provide a ratio of press shoe lengths of the shoe press unit associated with the first nip in the web travel direction, the middle shoe press unit, and the shoe press unit associated with the last nip in the web travel direction to be, e.g., approximately 3:2:1. Alternatively, the ratio may be, e.g., approximately 3.5:1.5:1.
Preferably, the linear forces generated in the various nips are at least substantially equal in magnitude. Alternatively, at least some of the linear forces generated in the various nips may be different from one another. In the latter case, the linear force generated in the first nip in the web travel direction may be advantageously less than the linear force generated in the last nip in the web travel direction, and the linear forces, in the web travel direction, preferably increase from one nip to the next in the web travel direction.
A relatively slight linear force in the first nip in the web travel direction has a decisive advantage in that more compact shoe press units, and, in the case of a shoe press roll, press rolls having lesser diameters may be utilized. In the case of a shoe press roll, the diameter may be, e.g., less than approximately one meter.
It is also especially advantageous if at least some of the resultant pressure profiles in the various nips are different from one another. This may involve either the pressure profiles that result crosswise (transverse) to the web travel direction, or to the pressure profiles that result in the web travel direction.
The lubrication of at least some of the various shoe press units, e.g., with oil, water or the like, may differ from the others.
The present invention can also be utilized when a given counterpart face is formed by a counter roll, and a plurality of shoe press units, e.g., two, are associated with that counter roll.
Accordingly, the present invention is directed to a press section of a machine for producing a fibrous web. The press section may include at least two shoe press units including at least one press shoe and a revolving flexible press belt, a counterpart face, at least two nips having a length extended in a web travel direction and formed by each at least one press shoe pressing the revolving flexible press belt against the counterpart face. A length of the extended nip may be at least substantially the same as a length of the at least press shoe length, measured in the web travel direction, forming the extended nip and at least one of the shoe press units having press shoe length different from the other shoe press units, whereby various extended nip length are formed.
In accordance with another feature of the present invention, the press shoe of the shoe press unit associated with a first nip in the web travel direction may have a length greater than the press shoe of the shoe press unit associated with a last nip in the web travel direction. Further, the press shoe of the shoe press unit associated with the first nip may have a length approximately two to five times greater than the press shoe of the shoe press unit associated with the last nip.
In accordance with another feature of the present invention, the press shoe of the shoe press unit associated with a first nip in the web travel direction may have a length less than the press shoe of the shoe press unit associated with a last nip in the web travel direction.
In accordance with still another feature of the present invention, the at least two extended nips may include at least three extended nips and at least three shoe press units. Further, the three shoe press units may include a first shoe press unit associated with a first nip in the web travel direction, a second press unit associated with a middle nip in the web travel direction, and a last press unit associated with a last nip in the web travel direction. The at least one press shoe of the first shoe press may have a length greater than the at least one press shoe of the middle shoe press and the at least one press shoe of the middle shoe press unit may have a length greater than the at least one press shoe of the last shoe press.
In accordance with a further feature of the present invention, the ratio of the lengths of the at least one press shoe of the first shoe press unit, the at least one press shoe of the middle shoe press unit, and the at least one press show of the last shoe press unit may be 3:2:1. Alternatively, the ratio of the lengths of the at least one press shoe of the first shoe press unit, the at least one press shoe of the middle shoe press unit, and the at least one press show of the last shoe press unit may be 3.5:1.5:1.
In accordance with another feature of the
Henssler Joachim
Loser Hans
Muellner Josef
Steiner Karl
Greenblum & Bernstein P.L.C.
Hastings Karen M.
Voith Sulzer Papiermaschinen GmbH
LandOfFree
Press section and method for pressing with different shoe... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Press section and method for pressing with different shoe..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Press section and method for pressing with different shoe... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2552128