Paper making and fiber liberation – Processes and products – Conditioning – preparing or repairing of apparatus
Reexamination Certificate
1999-03-05
2001-04-10
Hastings, Karen M. (Department: 1731)
Paper making and fiber liberation
Processes and products
Conditioning, preparing or repairing of apparatus
C162S272000, C162S300000, C162S301000
Reexamination Certificate
active
06214167
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
The present application claims priority under 35 U.S.C. § 119 of German Patent Application No. 198 09 480.9, filed on Mar. 6, 1998, 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 twin-wire former for producing a fibrous material web, e.g., a paper or cardboard web, from a fibrous suspension. The invention may also be related to further drainage of the fibrous material web. The present invention is based on a twin-wire former that includes two endless wire belts, e.g., a lower wire and upper wire, which jointly form a twin-wire zone. The upper wire is guided by at least two rolls, e.g., an inlet roll, which guides the upper wire to the twin-wire zone, and an outlet roll, which guides the upper wire back toward the inlet roll, and the upper and lower wires form a wedge-shaped inlet zone having an adjustable wedge angle. An upper wire subassembly, which includes a drainage box to receive suspension water flowing upwardly through the upper wire, as well as a common support device for the drainage box and for the inlet roll, is provided. The common support device can be pivoted via a stroke device around a horizontal “operational pivot” axle to vary the wedge angle during former operation.
2. Discussion of Background Information
Systems similar in general to the above-noted device have been discussed, e.g., in German Application No. 40 05 420, of which U.S. Pat. No. 5,045,153 is a patent family member; German Patent No. 43 26 867, of which U.S. Pat. No. 5,554,267 is a patent family member; and European Application No. 0 397 430, of which U.S. Pat. No. 5,074,964 is a patent family member.
The above noted documents, in contrast to the present invention, relate exclusively to so-called hybrid formers, in which a fibrous suspension flows onto the lower wire first. The web formation begins on the lower wire by removing water downwardly through the lower wire. Then the upper wire comes into contact with the remaining fibrous suspension in the twin-wire zone so that at this point, further web formation occurs via removing water upwardly through the upper wire, and, generally, downwardly through the lower wire. As a rule, the web formation is completed in the region of the twin-wire zone, i.e., there are no more free floating fibers, and, more often than not, from this point on, further drainage of the fibrous material web occurs to increase the dry matter content as much as possible.
In the twin-wire zone, it is possible, if necessary, to vary the inlet wedge angle (i.e., the angle of the wedge-shaped inlet zone) during operation so as to adapt the twin-wire former to various layer thicknesses of the incoming fibrous suspension. Sometimes, it is also desirable to move the point at which the upper wire comes into contact with the fibrous suspension, i.e., either in the web travel direction or in the opposite direction. To this end, it is known to pivot the upper wire subassembly with a stroke device around an operational pivot axle. In the known twin-wire formers, at least one additional (and costly) stroke device is provided to vertically adjust the position of the operational pivot axle. This adjustment via the additional stroke device is used for the purpose of lifting the upper wire subassembly up from the lower wire, e.g., to facilitate the changing of the wire and/or to prevent damage to the wires when there is an undesired stoppage of one of the two wires.
In the above-cited references, a number of different positions are provided for the operational pivot axle. According to a variant shown in
FIG. 2
of European Application No. 0 397 430, the operational pivot axle is located in the vicinity of the point at which the wires emerge from the drainage box (which is positioned inside the loop of the upper wire). This arrangement, which may be utilized in the twin-wire former according to the present invention, is favorable because, with a change of the inlet wedge angle, there is no horizontal motion of any consequence for the strips of the drainage box (which touch the upper wire) relative to the drainage elements located inside the lower wire loop. Such relative motion would impair the proper formation of the fibrous web. Also, the outlet end of the drainage box is prevented from vertical motion of any consequence, which would impair the proper travel of the two wires to the subsequent wire-separating device.
SUMMARY OF THE INVENTION
The present invention reduces the structural expenditure for the adjustment of the upper wire subassembly as compared to known twin-wire formers.
The instant twin-wire former of the present invention provides several desired features for a twin-wire former, e.g., a variable inlet wedge angle; and an upper wire subassembly which can be lifted up from the lower wire to prevent contact between the wires. The twin-wire former of the present invention is structured such that, as the inlet wedge angle is varied, horizontal movements of any consequence by the drainage box, which is located within the loop of the upper wire, and vertical movement of the outlet end of the drainage box, with the exception of negligible movement, are prevented.
The present invention provides a twin-wire former in which the stroke device, which is coupled to the common support device, is the sole stroke device. Thus, according to the present invention, the single stroke device is utilized to vary the wedge angle and to lift the upper wire subassembly up from the lower wire. Moreover, the upper wire subassembly is associated with an additional or second horizontal pivot axle located in a region of the outlet roll, so as to lift the upper wire subassembly up from the lower wire. An advantageous feature of the present invention is that the second pivot axle, which is located in the vicinity of the outlet roll, is also located in the vicinity of the point at which the wires emerge from the drainage box. In this manner, the upper wire subassembly may be pivoted upwardly and around the second pivot axle via the sole stroke device, which is preferably located in the vicinity of the inlet roll, to lift the upper wire subassembly up from the lower wire, thereby producing a gap between the two wires. According to the arrangement of the present invention, the second pivot axle is only effective after a maximal possible increase of the inlet wedge angle has taken place. By eliminating the necessity of an additional stroke device and the associated control therefore, considerable cost savings and simpler operability of the twin-wire former may be provided.
Further, another simplification is conceivable when only a single pivot axle is provided for the upper wire subassembly, and the single pivot axle is located in the region between the drainage box and the outlet roll. The upper wire subassembly may move around the single pivot axle, particularly when the inlet wedge angle is being changed. Moreover, if it is desired to reliably produce a gap between the two wires by even further lifting the upper wire subassembly, then the pivot axle may be preferably positioned in the region between the suction separator and the outlet roll. However, during inlet wedge angle changes with this arrangement, the outlet end of the drainage box may move slightly in the vertical direction.
Accordingly, the present invention is directed to a twin-wire former for producing a fibrous material web from a fibrous suspension that includes a twin-wire zone composed of a lower wire and an upper wire and a plurality of rolls including an inlet roll and an outlet roll. The upper wire is guidable over the plurality of rolls, the inlet roll is adapted to guide the upper wire to the twin-wire zone, and the outlet roll is adapted to guide the upper wire toward the inlet roll. A wedge-shaped inlet zone to the twin-wire zone is formed between the upper wire and the lower wire and has an adjustable inlet wedge angle. An upper wire subassembly includes a drainage bo
Banning Jurgen
Elenz Thomas
Halmschlager Gunter
Leitenberger Werner
Stelzhammer Franz
Greenblum & Bernstein P.L.C.
Hastings Karen M.
Voith Sulzer Papiertechnik Patent GmbH
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