Claims
- 1. A twin-wire web former in a paper machine, including an initial web forming portion followed by a twin-wire zone defined by first and second wires, comprising
- a first forming shoe having a ribbed deck arranged after the initial forming portion in a loop of one of said wires, said twin-wire zone beginning in the area of the ribbed deck,
- a pressure-loaded dewatering unit arranged after said first forming shoe in the running direction of the twin-wire zone, said dewatering unit comprising dewatering chambers on one side of said twin-wire zone and first and second sets of ribs situated on opposite sides of said twin-wire zone,
- a first one of said dewatering chambers having a suction-deflector duct, said first dewatering chamber arranged in opposed relationship to said first forming shoe for removing water that drains from the area of the ribbed deck through said suction-deflector duct,
- a second one of said dewatering chambers arranged after said first dewatering chamber in the running direction of said twin-wire zone, said second chamber having a lower part and a drain duct for drawing water into said second chamber,
- said first set of ribs being coupled to said lower part of said second dewatering chamber and defining gap spaces between ribs therein opening into said drain duct of said second dewatering chamber, said first set of ribs comprising dewatering and guide ribs, a first rib of said first set of ribs comprising a deflector rib defining a throat in a lower portion of said suction-deflector duct of said first dewatering chamber said first set of ribs further comprising a rib block defined after said first rib of said first set of ribs, said rib block leading into said drain duct of said second dewatering chamber and terminating with a last rib of said first set of ribs,
- said second set of ribs arranged opposite said first set of ribs on an opposite side of the twin-wire zone from the side of the twin-wire zone on which said first set of ribs are arranged, said second set of ribs comprising loading ribs with loading hoses, said loading ribs operative by means of pressure passed through said loading hoses and
- a loading unit arranged in a loop of said first wire after said first forming shoe in the running direction of the twin-wire zone, said loading unit comprising a frame part, said second set of ribs being arranged in said loading unit, said first set of ribs being arranged inside a loop of said second wire and comprising from 4 to 7 ribs, said second set of ribs comprising at least one fixed guide rib arranged in the twin-wire zone after said last rib of said first set of ribs in the runnina direction of the twin-wire zone, said at least one fixed guide rib being fixed to said frame part of said loading unit.
- 2. Web former of claim 1, wherein a single rib or a pair of ribs of said second set of ribs is arranged in opposed relationship to a lower surface of said first dewatering chamber before said first rib of said first set of ribs, a gap space being defined opposite said first dewatering chamber between said single rib or said pair of ribs of said second set of ribs, said first rib of said first set of ribs, said lower surface of said first dewatering chamber and said first forming shoe, said throat opening into said gap space to draw the water therefrom.
- 3. Web former of claim 2, wherein said loading unit comprises a frame box, said first forming shoe and/or said frame box of said loading unit being coupled to a source of negative pressure.
- 4. Web former of claim 1, wherein each of said first and second dewatering chambers communicates with a source of negative pressure so that the negative pressure present in said dewatering chambers is independently adjustable and/or regulatable, said dewatering chambers communicating with respective drain ducts only at a driving side of the web former.
- 5. Web former of claim 1 further comprising a replaceable form rib coupled to said first dewatering chamber and spaced from said twin-wire zone such that said replaceable form rib does not contact either one of said first and second wires, said throat being defined between said replaceable form rib and said first rib of said first set of ribs.
- 6. Web former of claim 5, wherein said first dewatering chamber has a lower part, the web former further comprising coupling means for connecting said replaceable form rib to an outer face of said lower wall of said first dewatering chamber, said coupling means comprising a groove-projection joint means arranged on respective surfaces of said lower wall of said first dewatering chamber and said replaceable form rib.
- 7. Web former of claim 1, further comprising a replaceable form rib arranged on said first dewatering chamber in opposed relationship to said first rib of said first set of ribs for dimensioning the size of said throat and/or adjusting the profile of said throat .
- 8. Web former of claim 1, wherein said initial web forming portion is a single-wire forming zone running in a plane, said twin-wire zone being curved downward on said curved ribbed deck of said first forming shoe from said plane of the single-wire initial portion, said twin-wire zone continuing in a downward inclined run guided by said first and second sets of ribs, said first set of ribs being arranged in a loop of said first wire,the web former further comprising
- a first forming roll arranged after said dewatering unit in said twin-wire zone inside the loop of said second wire, said first forming roll having a smooth solid face for curving said twin-wire zone into an upward inclined run,
- a second forming shoe arranged inside a loop of said first wire, said second forming shoe comprising a curved ribbed deck having a direction of curvature opposite to the direction of curvature of said first forming roll, said twin-wire zone being curved in the area of said ribbed deck of said second forming shoe, and
- a second forming roll arranged after said second forming shoe inside said loop of said first wire, said twin-wire zone being curved on said second forming roll into a downward inclined run, the curve radius of said second forming roll being smaller than the curve radius of said second forming shoe.
- 9. Web former of claim 8, further comprising
- a press roll arranged after said second forming roll inside said loop of said second wire, said press roll guiding said twin-wire zone to approach the plane in which said single-wire initial portion runs,
- first means for separating the web from said second wire so that the web follows said first wire, and
- second means for separating the web from said first wire in conjunction with a suction zone of a pick-up roll and transfer the web onto a pick-up fabric to carry the web into a press section.
- 10. Web former of claim 1, wherein the dry solids content of the web at a beginning of said twin-wire zone is from about 1.0% to about 3% , and the dry solids content of the web when it departs from said twin-wire zone is from about 8% to about 14%.
- 11. Web former of claim 10, wherein the dry solids content of the web at a beginning of said twin-wire zone is from about 1.2% to about 1.8% , and the dry solids content of the web when it departs from said twin-wire zone is from about 10% to about 12%.
- 12. Web former of claim 1, wherein a pair of ribs of said second set of ribs is arranged in opposed relationship to said first dewatering chamber before a first rib of said first set of ribs, the web former further comprising connecting means for connecting said pair of ribs of said second set of ribs.
- 13. An arrangement, for dewatering a web, in a twin-wire forming zone defined between first and second wires between which a web is dewatered and including a forming shoe comprising a curved ribbed deck and arranged in a loop of said first wire, comprising
- first dewatering means situated in opposed relationship to said forming shoe in a loop of said second wire, said first dewatering means comprising a first drain duct situated proximate to said forming shoe for drawing water that has been removed from the web in the area of said curved ribbed deck and a replaceable form rib arranged proximate to said first drain duct and spaced from the twin, wire zone such that said form rib does not contact either one of said first and second wires said form rib defining the size and shape of said first drain duct,
- second dewatering means arranged after said first dewatering means in the running direction of the twin-wire zone and in said loop of said second wire, said second dewatering means comprising a lower part and a second drain duct,
- a first set of ribs coupled to said lower part of said second dewatering means, said first set of ribs defining gap spaces between ribs opening into said second drain duct such that water from the web is passed through said gap spaces into said second drain duct, said first set of ribs comprising dewatering and guide ribs,
- a second set of ribs arranged substantially opposite said first set of ribs in said loop of said first wire, said second set of ribs comprising loading ribs for loading the twin-wire zone and means for loading/pressing said loading ribs, and
- connecting means for detachably connecting said form rib to a lower surface of said first dewatering means, said connecting means comprising a fastening base connected to said lower surface and a corresponding dovetail joint arranged in said form rib.
- 14. The arrangement of claim 13 wherein said second set of ribs comprise a pair of ribs arranged before a first rib of said first set of ribs and opposite a lower surface of said first dewatering means, said first rib of said first set of ribs comprising a deflector rib for doctoring water from an upper face of said second wire, a gap space being defined opposite said first dewatering means between said pair of ribs of said second set of ribs, said first rib of said first set of ribs, said lower surface of said first dewatering means and said curved ribbed deck, said first drain duct opening into said gap space to draw the water therefrom.
- 15. The arrangement of claim 13, wherein said first set of ribs and second set of ribs comprise replaceable ribs extending across the width of said upper and lower wires, said replaceable ribs comprising a wear-resistant material or having a wear-resistant front face which contacts the inner faces of said upper and lower wires.
- 16. A method for dewatering a web in a twin-wire forming zone defined between first wire and second wires and including a forming shoe comprising a curved ribbed deck arranged in a loop of said first wire, comprising the steps of:
- drawing water that has been removed from the web in the area of said curved ribbed deck into a first dewatering chamber via a first drain duct,
- providing a first set of ribs in a loop of said second wire,
- drawing water from the web through gap spaces defined between ribs in said first set of ribs into a second dewatering chamber via a second drain duct, said second dewatering chamber being arranged after said first dewatering chamber in the running direction of the twin-wire zone,
- arranging a second set of ribs in a loop of said first wire substantially opposite to said first set of ribs,
- loading said second set of ribs to press said first wire and force water from the web,
- arranging a form rib proximate said first drain duct and spaced from the twin-wire zone such that said replaceable form rib does not contact either one of said first and second wires said form rib defining the size and shape of said first drain duct and
- detachably connecting said form rib to a lower wall of Said first dewatering means by connecting a fastening base to said lower wall and arranging a corresponding dovetail joint in conjunction with said form rib.
- 17. The method of claim 16, further comprising the step of regulating the pressure applied to said second set of ribs in the running direction of the twin-wire zone and/or in a direction transverse to the running direction of the twin-wire zone.
- 18. A twin-wire web former in a paper machine, including an initial web forming portion followed by a twin-wire zone defined by first and second wires, comprising
- a first forming shoe having a ribbed deck arranged after the initial forming portion in a loop of one of said wires, said twin-wire zone beginning in the area of the ribbed deck,
- a pressure-loaded dewatering unit arranged after said first forming shoe in the running direction of the twin-wire zone, said dewatering unit comprising dewatering chambers on one side of said twin-wire zone and first and second sets of ribs situated on opposite sides of said twin-wire zone,
- a first one of said dewatering chambers having a suction-deflector duct, said first dewatering chamber arranged in opposed relationship to said first forming shoe for removing water that drains from the area of the ribbed deck through said suction-deflector duct, said suction-deflector duct of said first dewatering chamber comprising a throat part and said first dewatering chamber having a lower part,
- a second one of said dewatering chambers arranged after said first dewatering chamber in the running direction of said twin-wire zone, said second chamber having a lower part and a drain duct for drawing water into said second chamber,
- said first set of ribs being coupled to said lower part of said second dewatering chamber and defining gap spaces between ribs therein opening into said drain duct of said second dewatering chamber, said first set of ribs comprising dewatering and guide ribs,
- said second set of ribs arranged opposite said first set of ribs on an opposite side of the twin-wire zone from the side of the twin-wire zone on which said first set of ribs are arranged, said second set of ribs comprising loading ribs with loading hoses, said loading ribs operative by means of pressure passed through said loading hoses,
- a replaceable form rib coupled to said first dewatering chamber and spaced from said twin-wire zone such that said replaceable form rib does not contact either one of said first and second wires, said throat part of said suction-deflector duct being formed between said replaceable form rib and said twin-wire zone, and
- coupling means for connecting said replaceable form rib to an outer face of said lower part of said first dewatering chamber, said coupling means comprising a groove-projection joint means arranged on respective surfaces of said lower part of said first dewatering chamber and said replaceable form rib.
Priority Claims (2)
Number |
Date |
Country |
Kind |
920228 |
Jan 1992 |
FIX |
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932265 |
May 1993 |
FIX |
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Parent Case Info
This application is a continuation-in-part of U.S. Patent application Ser. No. 08/006,372 filed Jan. 19, 1993, now U.S. Pat. No. 5,395,484.
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Continuation in Parts (1)
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Number |
Date |
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Parent |
06372 |
Jan 1993 |
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