EP0373133A2 — Method and device in the formation of a paper or …

Claim 1

Independent Claim 501 words

Method for the formation of a paper or board web (W) out of a fibrous material, which said method is applied in the wire part of a paper machine or equivalent, which said wire part consists of a lower-wire loop (20), which is substantially horizontal at least at the initial end of its upper run, and of an upper-wire loop (10) jointly operative with said lower-wire loop, and in which said method the fibre suspension jet (J) arriving from the head box (19) of the paper machine is fed onto the initial part (20a) of the upper run of the lower-wire loop (20), said initial part constituting the first single-wire dewatering zone, whereupon the partly dewatered fibre layer is passed to the second dewatering zone, within whose area the upper-wire loop (10) is made to cover said partly dewatered fibre layer so that the dewatering of the fibre layer goes on in the area of the second dewatering zone, whereupon the upper-wire loop (10) is detached from the fibre web (W) formed, which is passed further to follow along with the run of the lower-wire loop (20) for the subsequent stages of treatment of the web (W), characterized in that, after the initial dewatering carried out in the single-wire dewatering zone (20a) through the lower wire (20), the fibre layer (W) that is being formed is passed over a lower-wire (20) support system (30) constituting a direct extension of said single-wire zone (20a), in the area of which said support system (30) dewatering by the effect of gravity through the lower wire (20) is prevented to a substantial extent, that the mode of web formation is chosen in accordance with the grammage of the quality that is being produced so that, when web qualities of higher grammage are being produced, after the single-wire dewatering zone (20a) the web (W) is passed to an initial part of the twin-wire dewatering zone, which is determined by the above support system (30) placed inside the lower-wire loop (20) and by a suction and foil equipment (40) placed opposite to it inside the upper-wire loop (10), the dewatering being carried out within said initial part mainly through the upper wire (10), and that, in a sec ond, alternative mode of web formation, when thinner web qualities are being produced, said suction and foil equipment (40) is placed apart from contact with the lower wire (20) placed facing it (Fig. 1), and that, after the above web formation stages, there follows a twin-wire dewatering section, taking place within a zone that is guided by a forming roll (16) or equivalent fitted inside the upper-wire loop (10) and curved upwards within a relatively short sector (a), whereupon the twin-wire forming zone is guided to be curved downwards, being guided by a forming shoe (26) or equivalent with a relatively large curve radius (A), and that, after the twin-wire forming zone, the web (W) is guided to follow one of the wires, most appropriately the lower wire (20).

Claim 2

Dependent Claim 501 words

Method for the formation of a paper or board web (W) out of a fibrous material, which said method is applied in the wire part of a paper machine or equivalent, which said wire part consists of a lower-wire loop (20), which is substantially horizontal at least at the initial end of its upper run, and of an upper-wire loop (10) jointly operative with said lower-wire loop, and in which said method the fibre suspension jet (J) arriving from the head box (19) of the paper machine is fed onto the initial part (20a) of the upper run of the lower-wire loop (20), said initial part constituting the first single-wire dewatering zone, whereupon the partly dewatered fibre layer is passed to the second dewatering zone, within whose area the upper-wire loop (10) is made to cover said partly dewatered fibre layer so that the dewatering of the fibre layer goes on in the area of the second dewatering zone, whereupon the upper-wire loop (10) is detached from the fibre web (W) formed, which is passed further to follow along with the run of the lower-wire loop (20) for the subsequent stages of treatment of the web (W), characterized in that, after the initial dewatering carried out in the single-wire dewatering zone (20a) through the lower wire (20), the fibre layer (W) that is being formed is passed over a lower-wire (20) support system (30) constituting a direct extension of said single-wire zone (20a), in the area of which said support system (30) dewatering by the effect of gravity through the lower wire (20) is prevented to a substantial extent, that the mode of web formation is chosen in accordance with the grammage of the quality that is being produced so that, when web qualities of higher grammage are being produced, after the single-wire dewatering zone (20a) the web (W) is passed to an initial part of the twin-wire dewatering zone, which is determined by the above support system (30) placed inside the lower-wire loop (20) and by a suction and foil equipment (40) placed opposite to it inside the upper-wire loop (10), the dewatering being carried out within said initial part mainly through the upper wire (10), and that, in a sec ond, alternative mode of web formation, when thinner web qualities are being produced, said suction and foil equipment (40) is placed apart from contact with the lower wire (20) placed facing it (Fig. 1), and that, after the above web formation stages, there follows a twin-wire dewatering section, taking place within a zone that is guided by a forming roll (16) or equivalent fitted inside the upper-wire loop (10) and curved upwards within a relatively short sector (a), whereupon the twin-wire forming zone is guided to be curved downwards, being guided by a forming shoe (26) or equivalent with a relatively large curve radius (A), and that, after the twin-wire forming zone, the web (W) is guided to follow one of the wires, most appropriately the lower wire (20).

Claim 3

Dependent Claim 82 words

Method as claimed in claim 1, characterized in that the zone that follows after the single-wire initial dewatering zone (20a) on the upper run of the lower wire is, in respect of its relatively long initial part, plane and constitutes a straight direct extension for the initial run (20a) of the lower wire of the former, and that on said initial part microturbulence is produced in the web (W) by means of grooves (35) or equivalent provided in the wire-support members (31).

Claim 4

Dependent Claim 191 words

Method as claimed in claim 1 or 2, characterized in that the set of suction and foil boxes (40) placed inside the upper-wire loop (10) is, together with at least the foremost guide roll (11a) of the upper wire (10), raised to an upper position (40′) when the former has been adjusted to operate in the range of lower grammages, as a rule 30...120 g/m² (Fig. 1), so that the twin-wire web forming zone starts on a short sector (a) of the hollow-faced (16′) forming roll (16) placed inside the upper-wire loop (10), and that when thicker paper qualities, as a rule within a grammage range of about 120...500 g/m², are produced, said part (75) of the upper-wire unit is pivoted to the lower position so that the wire support equipment (30) placed inside the lower-wire loop (20) and the suction and foil equipment (40), which is placed inside the upper-wire loop and which has been pivoted down (Fig. 2), for an initial section of the twin-wire dewatering zone, on which the dewatering is carried out primarily through the upper wire with the aid of said suction and foil equipment (40).

Claim 5

Dependent Claim 89 words

Method as claimed in claims 1 to 3, characterized in that on the forming roll (16) placed inside the upper-wire loop, the twin-wire zone is curved upwards within a short sector (a), whose magnitude is chosen within a range of a = 10 o ...45 o , most appropriately within a range of a = 15 o ...25 o , whereupon the twin-wire zone is curved downwards on a curved stationary shoe member (26), whose curve radius (R) is substantially larger than the radius of said forming roll (16).

Claim 6

Dependent Claim 101 words

Method as claimed in any of the claims 1 to 4, characterized in that after the zone (a) on the hollow-faced (16′) forming roll (16) placed inside the upper-wire loop, the twin-wire zone is curved downwards on a relatively short forming shoe (26A) with a relatively large curve radius (R A ), followed by a steeper downwardly curved zone, which is guided by means of a second forming roll (25) placed inside the lower-wire loop (20), and that hereupon the twin-wire zone is passed across one or several suction flatboxes (27) or equivalent placed inside the lower-wire loop (20) (Fig. 3).

Claim 7

Dependent Claim 58 words

Method as claimed in any of the claims 1 to 5, characterized in that in the method, after the upwardly curved zone occurring on the forming roll (16) on the twin-wire forming zone, in the dewatering taking place through the upper wire (10), a water collecting equipment (40A) fitted against the forming shoe (26) is employed (Fig. 4).

Claim 8

Dependent Claim 49 words

Method as claimed in any of the claims 1 to 6, characterized in that, when thicker web qualities are produced, before the beginning of the twin-wire forming zone, secondary pulp (J₁) is fed out of a secondary head box (60) to above the single-wire dewatering zone (20a) (Fig. 5).

Claim 9

Dependent Claim 318 words

Web forming device intended for carrying out the method as claimed in any of the claims 1 to 7, comprising a lower-wire loop (20) that has a substantially horizontal upper run and an upper-wire unit (70) jointly operative with said lower-wire loop and provided with an upper-wire loop (10), as well as a head box (19), which is arranged to feed the fibre suspension jet (J) onto the single-wire initial part (20a) of the upper run of the lower-wire loop, whereinafter a twin-wire forming zone is fitted, which is defined between the joint runs of the lower wire (20) and the upper wire (10), and within which said twin-wire forming zone there are various members and groups of members affecting the dewatering and placed inside the lower-wire loop (20) and the upper-wire loop (10), characterized in that, in its substantial and relatively long initial part, the twin-wire second dewatering zone is plane and constitutes a straight, direct extension of the single-wire initial part (20a), whereupon the twin-wire zone has been guided to be curved upwards, being guided by a short sector (a) of a forming roll (16) fitted inside the upper-wire loop and provided with a hollow face (16′), and hereinafter a forming shoe (26) is fitted inside the lower-wire loop (20), whose guide face, which is preferably provided with a ribbed deck (26′) and has a relatively large curve radius (R), guides the twin-wire zone to be curved downwards, and that inside the initial end of the upper-wire loop (10), a suction and foil equipment (40) is arranged, which is arranged so that it can be raised by means of actuators (17a,17b) from a lower operating position, which is used for the production of thick qualities, to an upper position (40′) when the former is adjusted for the production of thinner web qualities, as a rule within the grammage range of 30 to 120 g/m² (Fig. 1).

Claim 10

Dependent Claim 79 words

Device as claimed in claim 8, characterized in that on said straight initial section of the twin-wire dewatering zone, a forming board (30) is fitted, which comprises self-adjusted support beams (31) for the lower wire, which are placed inside the lower-wire loop (20) and which are, for their part, also fitted to act as means to prevent dewatering, and that, facing the forming board (30) and placed inside the upper-wire loop, a suction and foil equipment (40) is fitted.

Claim 11

Dependent Claim 69 words

Device as claimed in claim 8 or 9, characterized in that the forming board placed inside the lower-wire loop (20) consists of self-adjusted transverse beams (31) supported by loading hoses (32) or equivalent, said beams extending across the area facing the two or three suction chambers and their foil equipment (51,51′, 51˝) that guides the upper wire (10) in the dewatering equipment placed opposite to said transverse beams (31).

Claim 12

Dependent Claim 77 words

Device as claimed in any of the claims 8 to 10, characterized in that the suction and foil equipment (40) placed inside the upper-wire loop (10) consists of a set of boxes provided with at least two, most appropriately three, subsequent suction chambers (46,47,48), the foils (55,51′,51˝) placed in the bottom part of said set of boxes being fitted to guide the twin-wire dewatering zone as a straight and direct extension of the single-wire initial portion (20a).

Claim 13

Dependent Claim 60 words

Device as claimed in any of the claims 8 to 11, characterized in that before the suction and foil equipment (40), there is a suction-aided equipment whose upwardly inclined duct (46a) communicates with a first suction chamber (46), the mouth portion of said duct (46a) being provided with a profile rib (52) adjustable in relation to the upper wire (10).

Method and device in the formation of a paper or board web

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