Twin-wire former

A twin-wire former for the production of a fiber web from a fiber suspension, the former comprising:

• a first and a second paper machine wire belt moving in a web travel direction and forming a twin-wire zone for fiber suspension to move between the belts;
• a primary headbox for delivery of a fiber suspension to the twin wire zone;
• within the twin-wire zone, at the outer side of the first wire belt which is the side away from the second wire belt, a first plurality of rigid ledges arranged at a distance apart from each other, and a water removal box supporting the first ledges;
• within the twin-wire zone, a second plurality of ledges which lie opposite the first rigid ledges and which are at the outer side of the second wire belt which is the side away from the first wire belt;
• resilient support means supporting the second ledges to be pressed with selectable force against the second wire belt;
• the twin-wire zone having a region of commencement upstream with respect to the travel direction, a wire support surface at the outer side of at least one of the wire belts at the region of commencement of the twin-wire zone;
• the region in the travel direction where the first and second pluralities of ledges lie opposite each other, together with at least a part of the wire support surface, form a sandwich zone, the length of the wire support surface is in the range of 10% to 60% of the length of the sandwich zone, the position of the wire support surface is adjustable parallel to the direction of travel of the wire;
• the wire support surface includes a forming shoe having a slide surface thereon, the wire support surface is convexly curved with reference to the respective wire belt passing thereover and is rigidly supported on the twin-wire former, and the wire support surface is water impermeable.

A twin-wire former for the production of a fiber web from a fiber suspension, the former comprising:

• a first and second paper machine wire belt moving in a web travel direction and forming a twin-wire zone for fiber suspension to move between the belts;
• a primary headbox for delivery of a fiber suspension to the twin wire zone;
• within the twin-wire zone, at the outer side of the first wire belt which is the side away from the second wire belt, a first plurality of rigid ledges arranged at a distance apart from each other, and a water removal box supporting the first ledges;
• within the twin-wire zone, a second plurality of ledges which lie opposite the first rigid ledges and which are at the outer side of the second wire belt which is the side away from the first wire belt, resilient support means supporting the second ledges to be pressed with selectable force against the second wire belt;
• the twin-wire zone having a region of commencement upstream with respect to the travel direction, an essentially water-impermeable wire support surface at the outer side of at least one of the wire belts at the region of commencement of the twin-wire zone;
• resilient elements for pressing the wire support surface with selectable force against the respective wire belt at the outside of which the wire support surface is located, the resilient support for the wire support surface having moveable pressing ledges which extend transversely to the travel direction and resilient elements on which the moveable pressing ledges are supported, the twin-wire former including a stationary structure on which the resilient elements are guided;
• the wire support surface is a plate which rests loosely at the moveable pressing ledges, the plate having at least one stop by which it can be supported on the stationary structure of the twin-wire former with respect to movement of the plate with respect to the travel direction;
• and
• a roller rotatably mounted on the stationary structure and the stop on the plate being positioned to be supported with respect to movement with respect to the travel direction by the roller.

A twin-wire former for the production of a fiber web from a fiber suspension, the former comprising:

• a first and a second paper machine wire belt moving in a web travel direction and forming a twin-wire zone for fiber suspension to move between the belts;
• a primary headbox for delivery of a fiber suspension to the twin wire zone;
• within the twin-wire zone, at the outer side of the first wire belt which is the side away from the second wire belt, a first plurality of rigid ledges arranged at a distance apart from each other, and a water removal box supporting the first ledges;
• within the twin-wire zone, a second plurality of ledges which lie opposite the first rigid ledges and which are at the outer side of the second wire belt which is the side away from the first wire belt;
• resilient support means supporting the second ledges to be pressed with selectable force against the second wire belt;
• the twin-wire zone having a region of commencement upstream with respect to the travel direction, an essentially water-impermeable wire support surface at the outer side of at least one of the wire belts at the region of commencement of the twin-wire zone;
• resilient elements for pressing the wire support surface with selectable force against the respective wire belt at the outside of which the wire support surface is located, the resilient support for the wire support surface having moveable pressing ledges which extend transversely to the travel direction and resilient elements on which the moveable pressing ledges are supported, the twin-wire former including a stationary structure on which the resilient elements are guided;
• the wire support surface is a plate which rests loosely at the moveable pressing ledges, the plate having at least one stop by which it can be supported on the stationary structure of the twin-wire former with respect to movement of the plate with respect to the travel direction;
• a roller rotatably mounted on the stationary structure and the stop on the plate being positioned to be supported with respect to movement with respect to the travel direction by the roller;
• and
• the stop having a member tiltably mounted on the wire support plate.

A twin-wire former for the production of a fiber web from a fiber suspension, the former comprising:

• a first and a second paper machine wire belt moving in a web travel direction and forming a twin-wire zone for fiber suspension to move between the belts;
• a primary headbox for delivery of a fiber suspension to the twin wire zone;
• within the twin-wire zone, at the outer side of the first wire belt which is the side away from the second wire belt, a first plurality of rigid ledges arranged at a distance apart from each other, and a water removal box supporting the first ledges;
• within the twin-wire zone, a second plurality of ledges which lie opposite the first rigid ledges and which are at the outer side of the second wire belt which is the side away from the first wire belt, resilient support means supporting the second ledges to be pressed with selectable force against the second wire belt;
• the twin-wire zone having a region of commencement upstream with respect to the travel direction, an essentially water-impermeable wire support surface at the outer side of at least one of the wire belts at the region of commencement of the twin-wire zone;
• resilient elements for pressing the wire support surface with selectable force against the respective wire belt at the outside of which the wire support surface is located, resilient support for the wire support surface having moveable pressing ledges which extend transversely to the travel direction and resilient elements on which the moveable pressing ledges are supported, the twin-wire former including a stationary structure on which the resilient elements are guided;
• and
• tension springs supporting the wire support surface which is a plate on the stationary structure, and the spring force of the tension springs is selected to act against movement in the travel direction.

A twin-wire former for the production of a fiber web from a fiber suspension, the former comprising:

• a first and a second paper machine wire belt moving in a web travel direction and forming a twin-wire zone for fiber suspension to move between the belts;
• a primary headbox for delivery of a fiber suspension to the twin wire zone;
• within the twin-wire zone, at the outer side of the first wire belt which is the side away from the second wire belt, a first plurality of rigid ledges arranged at a distance apart from each other, and a water removal box supporting the first ledges;
• within the twin-wire zone, a second plurality of ledges which lie opposite the first rigid ledges and which are at the outer side of the second wire belt which is the side away from the first wire belt, resilient support means supporting the second ledges to be pressed with selectable force against the second wire belt;
• the twin-wire zone having a region of commencement upstream with respect to the travel direction, an essentially water-impermeable wire support surface at the outer side of at least one of the wire belts at the region of commencement of the twin-wire zone;
• resilient elements for pressing the wire support surface with selectable force against the respective wire belt at the outside of which the wire support surface is located, the resilient support for the wire support surface having moveable pressing ledges which extend transversely to the travel direction and resilient elements on which the moveable pressing ledges are supported, the twin-wire former including a stationary structure on which the resilient elements are guided;
• and
• a horizontal bending joint which extends transversely to the travel direction, and the wire support surface is a plate which is flexurally soft around the horizontal bending joint.

A twin-wire former for the production of a fiber web from a fiber suspension, the former comprising:

• a first and a second paper machine wire belt moving in a web travel direction and forming a twin-wire zone for fiber suspension to move between the belts;
• a primary headbox for delivery of a fiber suspension to the twin wire zone;
• within the twin-wire zone, at the outer side of the first wire belt which is the side away from the second wire belt, a first plurality of rigid ledges arranged at a distance apart from each other, and a water removal box supporting the first ledges;
• within the twin-wire zone, a second plurality of ledges which lie opposite the first rigid ledges and which are at the outer side of the second wire belt which is the side away from the first wire belt, resilient support means supporting the second ledges to be pressed with selectable force against the second wire belt;
• the twin-wire zone having a region of commencement upstream with respect to the travel direction, an essentially water-impermeable wire support surface at the outer side of at least one of the wire belts at the region of commencement of the twin-wire zone;
• resilient elements for pressing the wire support surface with selectable force against the respective wire belt at the outside of which the wire support surface is located, the resilient support for the wire support surface having moveable pressing ledges which extend transversely to the travel direction and resilient elements on which the moveable pressing ledges are supported, the twin-wire former including a stationary structure on which the resilient elements are guided;
• and
• a horizontal bending joint which extends transversely to the travel direction, and the wire support surface is a plate which is flexurally soft around the horizontal bending joint;
• the bending joint is in the region of one of the ledges and the plate has a groove on the side thereof toward the bending joint, the groove extending transversely to the travel direction.

A twin-wire former for the production of a fiber web from a fiber suspension, the former comprising:

• a first and a second paper machine wire belt moving in a web travel direction and forming a twin-wire zone for fiber suspension to move between the belts;
• a primary headbox for delivery of a fiber suspension to the twin wire zone;
• within the twin-wire zone, at the outer side of the first wire belt which is the side away from the second wire belt, a first plurality of rigid ledges arranged at a distance apart from each other, and a water removal box supporting the first ledges;
• within the twin-wire zone, a second plurality of ledges which lie opposite the first rigid ledges and which are at the outer side of the second wire belt which is the side away from the first wire belt;
• resilient support means supporting the second ledges to be pressed with selectable force against the second wire belt;
• the twin-wire zone having a region of commencement upstream with respect to the travel direction;
• an essentially water-impermeable wire support surface at the outer side of at least one of the wire belts at the region of commencement of the twin-wire zone;
• resilient elements for pressing the wire support surface with selectable force against the respective wire belt at the outside of which the wire support is located;
• and
• the wire support surface is a plate which includes a foil which is stretchable transversely to the travel direction, the foil is held under tension transversely to the travel direction, and is windable and unwindable.