EP0627523A1 - Doppelsiebformer in einer Papiermaschine - Google Patents

Doppelsiebformer in einer Papiermaschine Download PDF

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Publication number
EP0627523A1
EP0627523A1 EP94850085A EP94850085A EP0627523A1 EP 0627523 A1 EP0627523 A1 EP 0627523A1 EP 94850085 A EP94850085 A EP 94850085A EP 94850085 A EP94850085 A EP 94850085A EP 0627523 A1 EP0627523 A1 EP 0627523A1
Authority
EP
European Patent Office
Prior art keywords
wire
forming
unit
dewatering
gap
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP94850085A
Other languages
English (en)
French (fr)
Inventor
Heikki Ilvespää
Jyrki Jaakkola
Ari Linsuri
Erkki Partanen
Lauri Verkasalo
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Valmet Oy
Original Assignee
Valmet Paper Machinery Inc
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Valmet Paper Machinery Inc filed Critical Valmet Paper Machinery Inc
Publication of EP0627523A1 publication Critical patent/EP0627523A1/de
Withdrawn legal-status Critical Current

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Classifications

    • D—TEXTILES; PAPER
    • D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
    • D21F—PAPER-MAKING MACHINES; METHODS OF PRODUCING PAPER THEREON
    • D21F9/00—Complete machines for making continuous webs of paper
    • D21F9/003—Complete machines for making continuous webs of paper of the twin-wire type

Definitions

  • the invention concerns a gap former in a paper machine, comprising the loop of a carrying wire and the loop of a covering wire, which together form a twin-wire zone, which starts from the forming gap, into which the slice part of the headbox feeds the pulp suspension jet, and after which twin-wire zone the web is separated from the covering wire and is transferred on the carrying wire onto a pick-up fabric.
  • the object of the present invention is further development of the formers described in the applicant's FI Patent Application 751774 (equiv. to US Pat. 3,996,068) and FI Patent Applications 851650, 852662, and 902283, which formers are marketed by the applicant under the trade mark "Speed-Former".
  • the "Speed-Former” formers can be characterized as gap-roll-shoe formers.
  • need of further development has been noticed in particular in the case of papers made of slowly draining pulp qualities, such as SC-paper, and with particularly high machine speeds.
  • the former has been developed that is described in the applicant's said FI Pat. Appl. 902283, in whose gap-roll-shoe-roll former a considerable proportion of dewatering is carried out on the last (second) forming roll, in connection with which roll the necessary dewatering equipment is fitted so that, on the last forming roll, the dry solids content of the web is still raised by about 3...5 per cent.
  • the pulp suspension is passed from the headbox into a gap formed by a forming roll and by two wires, after which gap the two wires and the pulp layer placed between them follow the curve form of the forming roll, most of the water being drained through the wires.
  • the necessary dewatering pressure is produced by means of the tension of the outer wire, which tension produces a pressure in the pulp layer, which pressure is proportional to the wire tension and inversely proportional to the curve radius of the forming roll.
  • part of the kinetic energy of the pulp jet is converted to pressure energy, and the jet speed is lowered accordingly.
  • the dewatering through the outer wire away from the forming roll is intensified by the centrifugal force. Dewatering towards the forming roll can be intensified by means of negative pressure in a zone of the forming roll.
  • a roll-gap former is described, in which it has been considered novel that said dewatering unit or units comprise(s) a stationary press-support unit, which guides the wire that enters into contact with said unit as a substantially straight run, and that said dewatering unit or units comprise(s) a dewatering equipment placed facing said press and support unit and provided with a suction and foil equipment, said equipment removing a substantial amount of water out of the web.
  • twin-wire former One basic type of a twin-wire former is the so-called ribbed gap former, in which the discharge jet of the headbox is passed into the gap formed by two wires, which gap becomes narrower either as a substantially straight dewatering area formed by means of dewatering ribs placed at both sides of the wires transversely to their running direction or as one or two successive curved dewatering areas in which the ribs are placed at the side of the curve centre of the wires.
  • ribbed gap former in which the discharge jet of the headbox is passed into the gap formed by two wires, which gap becomes narrower either as a substantially straight dewatering area formed by means of dewatering ribs placed at both sides of the wires transversely to their running direction or as one or two successive curved dewatering areas in which the ribs are placed at the side of the curve centre of the wires.
  • the object of the present invention is further development of the prior art described above so that a novel gap former is provided by whose means both good formation of the web and good retention can be achieved.
  • an object of the invention is to provide a former in which the ratio of tensile strength machine direction / cross direction MD/CD of the paper produced can be made ever lower while, nevertheless, maintaining good formation and retention.
  • an object of the invention is to provide a former in which, if necessary, it is possible to achieve a ratio of tensile strength of the paper MD/CD ⁇ 2.5.
  • the twin-wire zone comprises a combination of the following web-forming and dewatering units, which are placed in the given sequence in the running direction of the web that is formed and which are known in themselves:
  • a suction box is placed either inside the carrying wire or inside the covering wire, as a rule preferably inside the carrying wire.
  • Figure 1 is a schematic side view of a former in accordance with the invention in which there is a vertically rising twin-wire zone and in which the open-faced forming roll in the gap area is placed inside the loop of the covering wire.
  • Figure 2 shows a twin-wire zone in the other respects similar to Fig. 1 except that the MB unit is in a position inverse in relation to Fig. 1.
  • Figure 3 is an illustration corresponding to Fig. 2 of a twin-wire zone in which the open-faced forming roll in the gap area is placed inside the loop of the carrying wire.
  • Figure 4 shows a twin-wire zone in the other respects similar except that the MB unit is placed in a position inverse in relation to Fig. 3.
  • Figure 5 shows a former in accordance with the invention in which the principal direction of the twin-wire zone is horizontal and the forming roll in the gap area is placed inside the loop of the upper wire, which operates as the covering wire.
  • Figure 6 shows the initial part of the twin-wire zone and the gap area in a former which is in the other respects similar to that shown in Fig. 5 except that the open forming roll is placed inside the loop of the lower wire, which operates as the carrying wire.
  • Figure 7 shows an exemplifying embodiment of a MB zone applied in the invention, which zone is in the other respects similar to that shown in Fig. 3 except that the forming shoe is placed inside the loop of the carrying wire.
  • Figure 7A shows the detail A indicated in Fig.7 on an enlarged scale.
  • the former comprises the loop of the covering wire 10 and the loop of the carrying wire 20. Between the lines B-C, the wires 10 and 20 form a twin-wire zone, in which water is removed from the web W through both of the wires 10,20.
  • the covering wire 10 is guided by the guide rolls 14,14' and by the first forming roll 11 or the corresponding breast roll 11A directly.
  • the forming gap G which becomes narrower as wedge-shaped, is defined between the covering wire 10, which is guided by the forming roll 11 or the corresponding breast roll 11A, and the carrying wire 20, which is guided by the forming roll 21 or the corresponding breast roll 21A.
  • the wires 10,20 have no common curve sector on the first forming roll 11;21, but the principal direction of the forming gap G and the joint run of the wires 10,20 following after the gap is straight until the inlet edge of the forming shoe 12,22.
  • the forming gap G is determined by the first open-faced 11';21' forming roll 11;21 and by the smooth-faced 11'';21'' breast roll 11A;21A, which is placed before said forming roll in the feed direction of the pulp jet J.
  • the forming gap G is defined, at one side, by the substantially straight run of the wire 10;20 from said breast roll 11A;21A to the inlet edge of the forming shoe 22 and, at the other side, by the opposite wire 20;10 curved on the open face 21';11' of the first forming roll 21;11, which opposite wire departs from the open face 21';11' of the forming roll 21;11 in the area of the bottom of the gap G.
  • the wire 10;20 runs on the open face 11';21' of the first forming roll 11;21, dewatering takes place into said open face 11';21' and through the substantially straight run of the opposite wire 20;10.
  • the twin-wire zone After the forming gap G, there is a curved forming shoe 12;22, which has a ribbed deck 12a;22a with a large curve radius R1.
  • the forming shoe 12;22 is followed by the MB unit 50 in the twin-wire zone, which unit consists of a dewatering unit 40 and a press and support unit 60 operating one opposite to the other, the wires 10,20 being pressed against one another by means of the latter unit so as to remove water out of the web W placed between the wires.
  • MB units 50 there may a higher number of said MB units 50, for example two, placed one after the other and preferably arranged so that in the successive units 50 the units 40 and 60 are placed inside different wire loops 10,20.
  • the MB unit 50 or units is/are followed by a suction box 29, which is provided with a ribbed deck and which is placed inside the loop of the carrying wire 20.
  • the suction box 29 is followed by a large-diameter D2 second forming roll 23, which is placed inside the carrying wire 20, which is a suction roll, and in which there are two successive suction zones 23a and 23b, according to Figs. 1 to 4, and one suction zone 23a, according to Fig. 5.
  • the diameter D2 of the second forming roll 23 is, as a rule, chosen in the range of D2 ⁇ 1.0...2.0 m.
  • the covering wire 10 is separated at the line C from the covering wire 20 by means of the guide roll 14', the web W following said carrying wire 20. According to Figs.
  • the web W is passed further on the suction zone 24a of the wire 20 suction roll 24 and from there further as downwards inclined to the pick-up point, where the web W is transferred onto the pick-up fabric 31 on the suction zone 30a of the pick-up roll 30.
  • the carrying wire 20 continues its run, guided by the guide rolls 24, onto the breast roll 21A in the gap area (Figs. 1, 2 and 5) or onto the forming roll 21 placed in the gap area, which forming roll has an open face 21' which receives water (Figs. 3 and 4).
  • the main direction of the run of the twin-wire zone B-C is vertical.
  • the twin-wire zone starts in the forming gap G, into which the slice part 32 of the headbox feeds the pulp suspension jet J.
  • the jet J is directed towards the bottom of the straight gap G which becomes narrower as wedge-shaped.
  • a forming roll that is provided with an open face 11' and that receives water.
  • a breast roll 21A On a level lower than said forming roll 11, at the distance of the height difference h1, inside the loop of the carrying wire, there is a breast roll 21A provided with a smooth solid face 21''.
  • the diameters D1 of the rolls 11 and 21A are preferably substantially equal in comparison with one another, being of an order of D1 ⁇ 0.5...1.5 m, preferably D1 ⁇ 0.7...1.0 m.
  • said difference in height h1 is preferably in the range of h1 ⁇ 50...300 mm.
  • the forming roll 11 may also be a suction roll provided with an inside suction chamber 11a, the negative pressure employed in said roll being preferably in the range of p0 ⁇ 10...20 kPa.
  • the outlet end of the forming gap G is in the horizontal plane T-T determined by the central axis of the first forming roll 11 or near said plane.
  • the water-receiving forming roll 21 provided with an open face 21' is placed inside the loop of the carrying wire 20, and the breast roll 11A provided with a smooth face 11'' is placed inside the loop of the covering wire 10.
  • the forming roll 11;21 is arranged so that its position can be adjusted substantially in the horizontal plane (arrow E).
  • the gap area is substantially immediately followed by the forming shoe 12;22.
  • the forming shoe 12 shown in Figs. 3 and 4 is placed inside the loop of the covering wire 10, and the forming shoe 22 shown in Figs. 1,2,5 and 6 is placed inside the loop of the carrying wire 20.
  • the forming shoes 12;22 are provided with a ribbed deck of a large curve radius R1.
  • the curve radius R1 is usually chosen within the range of R1 ⁇ 2...8 m, preferably in the range of R1 ⁇ 3...5 m.
  • the box of the forming shoe 12;22 may be connected to negative pressure p3, which is illustrated by the corresponding arrow in Fig. 1.
  • the negative pressure p3 promotes the draining through the gaps in the ribbed deck 12a;22a.
  • the forming shoe 12;22 is substantially immediately followed by the MB unit 50, which, according to Fig. 1, comprises two draining chambers 40a and 40b, which are fitted inside the loop of the covering wire 10, which are separated from one another by a partition wall 49, and both of which communicate with different negative pressures p1 and p2.
  • the press and support unit 60 is provided with a corresponding set of ribs 70, and the construction and the operation of said sets of ribs 70,80 will be described in more detail later with reference to Figs. 7 and 7A.
  • the box 61 in the press and support unit 60 can also, if necessary, be connected to negative pressure p4.
  • the units 40 and 60 operating one opposite to the other in the MB unit 50 are placed in an inverse order, compared with Fig. 1, so that in Fig. 2 the dewatering unit 40 is placed inside the loop of the carrying wire 20 and the press and support unit 60 is placed inside the loop of the covering wire 10.
  • the MB unit 50 or units is/are followed by a suction box 19, which is fitted inside the loop of the covering wire 10 and which is provided with a ribbed deck provided with slots and operating against the inner face of the wire 10.
  • the dewatering unit 40 of the MB unit 50 is placed inside the loop of the carrying wire 20, and the press and support unit 60 inside the loop of the opposite wire 10, whereas in Fig. 4, compared with Fig. 3, the units 40 and 60 are placed in an inverse order.
  • the principal direction of the twin-wire zone guided by the sets of ribs 80,70 in the units 40 and 60 is straight, but alternatively it is possible to use a ribbed zone 70,80 whose principal direction is slightly curved, the curve radius of said zone being denoted with R2 in Figs. 1 and 2.
  • Said curve radius R2 is, as a rule, chosen within the range of R2 ⁇ 3...8 m.
  • the centre of curvature of R2 is placed at the side of the dewatering unit 40, and in Fig. 2 at the side of the press and support unit 60.
  • Figs. 5 and 6 show two horizontal versions of a gap former in accordance with the invention.
  • the gap G is determined by the lower breast roll 21A, which has a smooth solid face 21'', and by the upper forming roll 11, which is provided with an open face 11' that receives water. Between the rolls 21A and 11, there is a horizonal distance v1.
  • the upper forming roll 11 has been arranged adjustable mainly in the vertical direction (arrow E) in view of fine adjustment of the gap geometry.
  • arrow E the vertical direction
  • a breast roll 11 provided with a smooth face 11' and a lower forming roll 21 which is provided with an open face 21', the horizontal distance between said rolls being v1, which is, as a rule, in the range of v1 ⁇ 50...300 mm.
  • the forming gap G is followed by a forming shoe 22 placed inside the loop of the lower wire 20, which forming shoe is provided with a ribbed deck 22a of a curve radius R1.
  • the MB unit 50 which comprises a first water drain chamber 41, placed above the forming shoe 22 inside the loop of the upper wire 10 in the way shown in Fig. 6, said chamber having a water drain duct 42 preferably at the driving side of the machine only.
  • a gap space 43 remains, through which the water is drained, aided by negative pressure p1, through the suction-deflector duct 44 in the direction of the arrow V1 into the chamber 41 and from it further through the duct 42 to the side of the paper machine and into the wire pit.
  • the suction-deflector duct 44 In the direction of the arrow V1, through the suction-deflector duct 44, mainly water that has been separated from the web W through the upper wire 10 in the area of the shoe 22 is drained.
  • the first water drain chamber 41 is followed directly by a second water drain chamber 45, in connection with whose rear wall there is a water drain duct 47.
  • a set of ribs 70 operates which is loaded by means of the pressure of the pressure medium of the press and support unit 60, and the construction and the operation of said sets of ribs 70,80 will be described in more detail in the following with reference to Figs. 7 and 7A.
  • the MB unit 50 or units is/are followed by a suction box 29, which is placed inside the loop of the carrying wire 20 and which is provided with a ribbed deck that includes slots.
  • a suction box 29 After the suction box 29, the twin-wire zone is curved in the suction zone 23a of the second forming roll 23 to become downwards inclined, and the web W is separated from the upper wire 10 and guided to follow the lower wire 20, being assured by the negative pressure present in the ribbed deck 25a of the suction box 25 placed inside the loop of the lower wire 20.
  • Figs. 7 and 7A directly after the curved ribbed deck 22a of the forming shoe 22 and inside the loop of the carrying wire 20, the dewatering unit 40 of the MB unit 50 is fitted. Inside the loop of the covering wire 10, there is the press and support unit 60 of the MB unit 50, whose construction comes out in more detail from Fig. 7A.
  • the unit 60 includes a set of ribs 70, which consists of ceramic loading ribs 71,72, which are interconnected in pairs by means of support structures 73.
  • the ribs 71,72, and so also their back-up ribs 81, extend in the transverse direction across the entire width of the web W and of the wires 10,20.
  • the set of ribs 70 is loaded by means of pressures p k passed into the loading hoses 75 against the stationary frame constructions 74. Into the hoses 75, pressures p k are passed through the pipes 77 out of the source 76 of negative pressure, which is illustrated just schematically.
  • the units 40 and 60 may also change places with one another.
  • the set of ribs 80 of the equipment 40 placed inside the loop of the carrying wire 20 consists of forming ribs 81, which are attached to the frame constructions 84 by means dovetail joints.
  • the ribs 81 are placed as alternating with, not directly opposite to, the ribs 71,72 in the set of ribs 70 so that, being guided by the sets of ribs 70,80, the twin-wire zone runs between the units 40,60 along a very gently meandering path, whose principal direction is straight or curved and whose curve radius is, in Figs. 1 and 2, denoted with R2.
  • the dewatering can be intensified by means of the effect of negative pressures p1,p2,p4 present in the gaps between the ribs 71,72,81.
  • the symmetry of dewatering and of web formation can be controlled by means of regulation of said levels of negative pressure p1,p2,p3,p4 in the units 40 and/or 60.
  • the dewatering equipment 40 has been divided by a partition wall 49 into two compartments 40a and 40b, each of which communicates separately with a suction pump, so that the compartments 40a and 40b can be provided with negative pressures p1 and p2 of different levels to promote the dewatering.
  • Fig. 1 the dewatering proportions at the different dewatering units are illustrated by the arrows F1,F2,F3,F4,F5,F6,F7 and F8.
  • One particularly favourable distribution of the dewatering proportions that can be accomplished in a former in accordance with the invention is the following: F1 ⁇ 15 % F2 ⁇ 27 % F3 ⁇ 20 % F4 ⁇ 4 % F5 ⁇ 29 % F6 ⁇ 1 % F7 ⁇ 3,5 % F8 ⁇ 0,5 %
  • a symmetric and equal dewatering is achieved through both of the wires 10 and 20, whereby the symmetry of the web structure is promoted. It is an essential feature and a difference compared with the applicant's prior-art "Speed-Former" concept that, in the invention, water is removed on the former roll 11;21 to a considerably lower extent than in the "Speed-Former", which contributes to an improved retention.
  • the consistencies i.e. dry solids contents of the web that is being formed, which are indicated in Fig. 3, are preferably as follows:
  • the various parameters in accordance with the invention that affect the web formation are preferably chosen so that the dry solids contents k1...k4 defined above and given in the following table will be carried into effect.
EP94850085A 1993-05-18 1994-05-17 Doppelsiebformer in einer Papiermaschine Withdrawn EP0627523A1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
FI932264 1993-05-18
FI932264A FI932264A (fi) 1993-05-18 1993-05-18 Paperikoneen kitaformeri

Publications (1)

Publication Number Publication Date
EP0627523A1 true EP0627523A1 (de) 1994-12-07

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EP94850085A Withdrawn EP0627523A1 (de) 1993-05-18 1994-05-17 Doppelsiebformer in einer Papiermaschine

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EP (1) EP0627523A1 (de)
CA (1) CA2123820A1 (de)
FI (1) FI932264A (de)

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0894893A2 (de) * 1997-08-01 1999-02-03 Voith Sulzer Papiermaschinen GmbH Doppelsiebformer
WO1999060205A1 (en) * 1998-05-18 1999-11-25 Valmet Corporation Twin-wire roll-gap former in a paper machine
DE10022110A1 (de) * 2000-05-08 2001-11-22 Dieter Ronnenberg Beeinflussung eines Bahneigenschafts-Profiles mittels mindestens eines Schallfeldes
EP1233105A2 (de) * 2001-02-14 2002-08-21 Voith Paper Patent GmbH Doppelsiebformer
EP1568820A1 (de) * 2004-02-26 2005-08-31 Voith Paper Patent GmbH Blattbildungssystem
US8048269B2 (en) 2006-06-28 2011-11-01 Metso Paper, Inc. Forming section

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FI953984A (fi) * 1995-08-24 1997-02-25 Valmet Corp Paperikoneen rainanmuodostusosa

Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE9105797U1 (de) * 1991-05-10 1991-07-04 J.M. Voith Gmbh, 7920 Heidenheim, De
EP0504123A1 (de) * 1991-03-15 1992-09-16 Valmet Paper Machinery Inc. Doppelsiebpartie einer Papiermaschine
DE9115632U1 (de) * 1991-12-17 1992-11-12 J.M. Voith Gmbh, 7920 Heidenheim, De
EP0515964A1 (de) * 1991-05-29 1992-12-02 J.M. Voith GmbH Doppelsiebformer für eine Papiermaschine
WO1993002250A1 (en) * 1991-07-19 1993-02-04 Valmet-Tampella Inc. Two-wire web-forming section of a paper machine
EP0552139A1 (de) * 1992-01-17 1993-07-21 Valmet Paper Machinery Inc. Blattbildungspartie für eine Papiermaschine

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0504123A1 (de) * 1991-03-15 1992-09-16 Valmet Paper Machinery Inc. Doppelsiebpartie einer Papiermaschine
DE9105797U1 (de) * 1991-05-10 1991-07-04 J.M. Voith Gmbh, 7920 Heidenheim, De
EP0515964A1 (de) * 1991-05-29 1992-12-02 J.M. Voith GmbH Doppelsiebformer für eine Papiermaschine
WO1993002250A1 (en) * 1991-07-19 1993-02-04 Valmet-Tampella Inc. Two-wire web-forming section of a paper machine
DE9115632U1 (de) * 1991-12-17 1992-11-12 J.M. Voith Gmbh, 7920 Heidenheim, De
EP0552139A1 (de) * 1992-01-17 1993-07-21 Valmet Paper Machinery Inc. Blattbildungspartie für eine Papiermaschine

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0894893A2 (de) * 1997-08-01 1999-02-03 Voith Sulzer Papiermaschinen GmbH Doppelsiebformer
EP0894893A3 (de) * 1997-08-01 1999-07-14 Voith Sulzer Papiermaschinen GmbH Doppelsiebformer
WO1999060205A1 (en) * 1998-05-18 1999-11-25 Valmet Corporation Twin-wire roll-gap former in a paper machine
DE10022110A1 (de) * 2000-05-08 2001-11-22 Dieter Ronnenberg Beeinflussung eines Bahneigenschafts-Profiles mittels mindestens eines Schallfeldes
DE10022110B4 (de) * 2000-05-08 2007-10-25 Dieter Ronnenberg Beeinflussung eines Bahneigenschafts-Profiles mittels mindestens eines Schallfeldes
EP2345761A2 (de) 2000-05-08 2011-07-20 Dieter Ronnenberg Verfahren und Vorrichtung zur Bearbeitung einer Faserstoffbahn oder einer Suspensionsschicht
EP1233105A2 (de) * 2001-02-14 2002-08-21 Voith Paper Patent GmbH Doppelsiebformer
DE10106731A1 (de) * 2001-02-14 2002-08-22 Voith Paper Patent Gmbh Doppelsiebformer zur Herstellung einer Faserstoffbahn aus einer Faserstoffsuspension
EP1233105A3 (de) * 2001-02-14 2003-12-03 Voith Paper Patent GmbH Doppelsiebformer
US6776877B2 (en) 2001-02-14 2004-08-17 Voith Paper Patent Gmbh Twin wire former for the production of a fiber web from a fiber suspension
EP1568820A1 (de) * 2004-02-26 2005-08-31 Voith Paper Patent GmbH Blattbildungssystem
US8048269B2 (en) 2006-06-28 2011-11-01 Metso Paper, Inc. Forming section

Also Published As

Publication number Publication date
CA2123820A1 (en) 1994-11-19
FI932264A (fi) 1994-11-19
FI932264A0 (fi) 1993-05-18

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