Paper making and fiber liberation – Apparatus – Running or indefinite length product forming and/or treating...
Patent
1996-09-13
1999-06-22
Hastings, Karen M.
Paper making and fiber liberation
Apparatus
Running or indefinite length product forming and/or treating...
162300, D21F 100
Patent
active
059140097
DESCRIPTION:
BRIEF SUMMARY
The invention concerns a double-wire sheet former of a paper machine for creating a paper web between two sandwiched wires.
Sheet formers are known in the art. Reference is made to G 92 01 722.3.
A shortcoming of the known double-wire sheet formers is that, among others because of their overall height and excessive rebuilding expense, they are poorly suited for rebuilding.
The problem underlying the invention is to present double-wire sheet formers which eliminate the disadvantage of the prior art.
This problem is solved by the features of the present invention.
A double-wire sheet forming part of a paper machine begins with a forming roll in the bottom wire and a solid-shell roll in the top wire. The forming roll may be or may not be equipped with suction. Both rolls form jointly a gap. Top and bottom wire wrap jointly around the forming roll on an arc of 30 to 65.degree.. A machinewide stream of suspension injects into the gap formed by the breast roll and the forming roll and, due to wire pressure and vacuum, is partly dewatered by both wires, creating two uniformly formed external layers. The water issuing out of the outer wire is by a stream guide trough channeled into a chute, backed by vacuum. The two wires proceed approximately horizontally after the forming roll.
The further sheet formation takes place in a turbulence section formed by a vacuum box with individual slats and a forming box in the bottom wire. The forming box is fitted with individual forming slats adapted for pneumatic contacting.
The two wires are separated in known fashion by a curved suction separator. The bottom wire after the suction separator resembles a fourdrinier wire with a suction flatbox, wire suction roll and wire drive roll.
A fundamental, common characteristic of all proposed sheet formers is an essentially horizontal arrangement of the sheet forming zone, making them in their illustrated form particularly suited for replacement of existing fourdrinier wires or for rebuilding an existing fourdrinier wire to a double-wire former.
BRIEF DESCRIPTION OF THE DRAWINGS
For detail explanation, embodiments are illustrated in FIG. 1 through 7.
DETAILED DESCRIPTION
FIG. 1 shows a fourdrinier wire rebuilt into a double-wire sheet former with the lower revolving wire 2 and, arranged so as to lie above it, the wire 1 revolving above. The wire 1 is deflected over several deflection rolls and passed to a first breast roll 3 which is situated approximately at an angle of 45.degree. to the left and above the first entry roll 4 of the bottom wire 2, which is fashioned as a forming roll. Between the roll 3 and roll 4, the stock suspension is injected by the headbox between the wires 1 and 2. Following the roll 4, a first dewatering shoe 6 having a slight curvature corresponding to the roll 4 is arranged on the side of the wire 2. Following the forming shoe 6 is a double dewatering unit 7.1 and 7.2, for example according to the U.S. Pat. No. 5,045,153 (P 4713), the dewatering unit 7.2 being a suction box with a plurality of rigid slats 7.4 that are situated on the side of wire 1. Arranged opposite from it is the dewatering unit 7.1, which is equipped with a plurality of dewatering slats 7.3 that are staggered relative to the opposing slats 7.4 of unit 7.2. Essential is that at least part of the slats 7.3 of unit 7.1 are supported by means of flexible elements, for instance springs or pneumatic pressure cushions (as indicated schematically) and that, preferably, each individual slat can be forced down on the wire 2 with a selective force. Reference is made to the U.S. Pat. No. 5 078 835 (P 4734). The radius of curvature in the center of wire units 7.2 and 7.1 is situated on the other side of the wires, relative to the radius of curvature of the wire unit 6. Following the wire units 7.1, 7.2, a separating unit with opposite curvature, in the form of a suction shoe, is arranged again on the side of wire 2. Separating from the web in the area of shoe 8, the wire 1--proceeding over a deflection roll 11 and further deflection rolls--retur
REFERENCES:
patent: 4554052 (1985-11-01), Waris
patent: 5045153 (1991-09-01), Sollinger et al.
patent: 5078835 (1992-01-01), Schiel et al.
patent: 5167770 (1992-12-01), Bubik et al.
patent: 5215628 (1993-06-01), Koivuranta et al.
patent: 5282933 (1994-02-01), Bubik et al.
patent: 5389206 (1995-02-01), Buck et al.
patent: 5599427 (1997-02-01), Koivuranta et al.
Das Papier; Gap Forming Technology with TWIN-Former G for Testliner and Corrugating Medium; Muller, Bubik and Schaible; Jul. 1991, pp. 347-354.
Hastings Karen M.
J.M. Voith & GmbH
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