Valmet Paper Machinery Inc.

Valmet Corporation

Mauri Koivuranta

Michael H Odell

Lauri Verkasalo

Erkki Partanen

The invention is related to a twin-wire web former in a paper machine having a covering wire and a carrying wire which form a twin-wire forming zone with one another. A discharge opening of a headbox feeds a pulp suspension jet into the forming gap defined between said wires. The forming gap is immediately followed immediately by a forming shoe provided with a curved guide deck. A draining unit or units is/are provided after the forming shoe, before the first forming roll. The draining unit/units comprise(s) a press/support unit which guides the wire placed in contact with it as a straight run. The draining unit or units further comprise(s) a draining equipment provided with suction and foil equipment and placed opposite to the press/support unit, which draining equipment removes a substantial amount of water out of the web.

Twin-wire web former in a paper machine

A twin-wire web former in a paper machine includes a covering wire and a carrying wire defining a forming zone, at the beginning of which zone there is a forming gap into which the discharge opening of a headbox feeds a pulp suspension jet. A first forming roll is located on the twin-wire zone, in the area of the forming gap, on which the twin-wire zone is curved within a certain sector, followed by a dewatering unit(s), which is in turn followed by a second forming roll(s) in the twin-wire zone. Thereafter, the web is detached from the covering wire and passed on the carrying wire to a pick-up point. Between the first forming roll and the second forming roll(s), a dewatering unit(s) is provided which comprises a press-support unit which guides the wire that enters into contact with the unit as a straight run. The dewatering unit(s) also includes a dewatering equipment facing the press-support unit and provided with suction and foil equipment for removing a substantial amount of water out of the web. The magnitude of the twin-wire turning sector placed in connection with the first forming roll is within the range of from about 35.degree. to about 120.degree..

A gap former in a paper machine, comprising a lower wire loop (10) and an upper wire loop (20), which together define a substantially horizontal twin wire forming zone, which comprises the following web forming zones (a), (b) and (c): (a) In the area of the forming gap (G), a first suction zone (11a) placed inside the first forming roll (11), and immediately thereafter a second suction zone (11b) is placed in forming roll (11). The suction zones (11a, 11b) are placed in the first upper quarter of the first forming roll (11) at the side of the forming gap (G). The levels of negative pressure (P.sub.1, P.sub.2) in the suction zones are adjustable. (b) A forming shoe (12), which is provided with an open guide deck (26), the interior space in the shoe being divided into at least two subsequent suction chambers (12a, 12b, 12c), the levels of negative pressure (P.sub.a, P.sub.b, P.sub.c) effective in said suction chambers being arranged to be adjustable, preferably separately adjustable. (c) Web-formation and/or guide members (13a, 13b, 17, 25) arranged after the forming shoe (12), the members guiding the twin wire zone downwards.

Gap former in a paper machine

Hybrid former for a paper machine which has a lower-wire loop forming a single-wire dewatering zone in which water is removed from a web being formed by a dewatering member situated inside the wire loop through the lower wire. The former also has an upper-wire unit which includes an upper-wire loop forming a second twin-wire dewatering zone after the first single-wire dewatering zone, together with a run of the lower wire. The former additionally includes a hollow-faced first forming roll fitted inside the upper-wire loop, at which the second, twin-wire dewatering zone starts, this zone being curved upwardly over a certain sector of this forming roll. A forming shoe is fitted inside the lower-wire loop after the forming roll and guides the second dewatering zone. This forming shoe is provided with a curved deck for guiding the lower-wire loop. Deflector units are fitted both inside the lower-wire loop and inside the upper-wire loop on the twin-wire dewatering zone between the first forming roll and the forming shoe. By way of these deflector units, sufficiently strong impulses improving the formation of a web are produced, which act upon the web that is being formed from both sides thereof.

Growing community of inventors

Petajavesi, Finland

Mauri Koivuranta