Patent ID: 7931777
Filing Date: 2011-04-26
Classification: D21F

Abstract:
1. A method of forming a multi-layer web in a formation section, comprising the steps of: forming a first partial web on a first wire of a first wire unit with a pulp suspension jet supplied by a first headbox at a forward end of the first wire unit; guiding the first wire of the first forming unit and the first partial web formed thereon through a second wire unit, successive to the first wire unit, so that the first wire of the first wire unit meets a second wire of the second wire unit and defines a two-wire stretch with the second wire in the second wire unit, the two-wire stretch defining a forward end of the two wire stretch where the first wire meets the second wire, and a first side defined by the first wire and a second side defined by the second wire; forming a second pulp layer atop the first partial web with a second pulp suspension jet supplied by a second headbox, at a forward end of the second wire unit; subjecting the second pulp layer atop the first partial web to non-pulsating dewatering in at least a first dewatering zone of the two-wire stretch of the second wire unit, with a fixed formation shoe having a leading edge and a curved cap, which shoe is located at the forward end of the two-wire stretch, wherein the non-pulsating dewatering takes place by moving the twin wire stretch and the first partial web with the second pulp layer atop over the curved cap which is placed against the second side of the two-wire stretch, wherein the first partial web with second pulp layer atop is subjected to non-pulsating dewatering in the first dewatering zone by drawing water from the first partial web with second pulp layer atop through openings in the cap formed by holes or by gaps essentially in the lengthwise direction of the machine which extend through the cap, and affecting the dewatering of the first partial web with the second pulp layer atop with an under-pressure through the openings of the cap in an area following after the leading edge of the fixed formation shoe so that the leading edge of the fixed formation shoe does not remove water from the first partial web with the second pulp layer atop; subjecting the first partial web with second pulp layer atop to pulsating dewatering in a second and downstream dewatering zone in the two-wire stretch of the second wire unit with fixed dewatering lists which are placed against the first side or the second side of the two-wire stretch, the fixed lists extending in the cross machine direction and between which there are gaps which extend in a cross machine direction, through which gaps under-pressure is drawn whereby the first partial web with the second pulp layer atop travelling in between the wires of the two-wire stretch is subjected to pulsating dewatering by the fixed dewatering lists, and by under-pressure in the gaps of the fixed dewatering lists; wherein the step of subjecting the first partial web with second pulp layer atop to pulsating dewatering in the second and downstream dewatering zone includes controllably loading a plurality of moveable lists against the first side or the second side of the two-wire stretch, opposite the fixed dewatering lists, at the gaps between the fixed dewatering lists; wherein the step of forming the first partial web on the first wire with the pulp suspension jet comprises supplying the suspension jet in to a jaw at a forward end of the first wire unit, the jaw being defined by the first wire and a superpostioned wire forming a first two-wire stretch, the first two wire stretch defining a beginning where the first wire and the superpostioned wire first meet; accomplishing dewatering in a first dewatering zone of the first wire unit as non-pulsating dewatering with another fixed formation shoe having a leading edge and a curved cap, which shoe is located at the beginning of a first two-wire stretch formed of the first wire and an another wire, wherein the non-pulsating dewatering takes place by moving the first two-wire stretch over the curved cap which is placed against one side of the first two-wire stretch, wherein fiber pulp traveling in-between the first wire and the another wire is non-pulsatingly dewatered in the first dewatering zone by drawing water from the fiber pulp traveling in-between the formation wires through openings in the cap which extend through the cap, and affecting the dewatering of fiber pulp traveling in-between the first wire and the another wire with an under-pressure effected through the openings of the cap in an area following after the leading edge so that the leading edge of the fixed formation shoe does not remove water from the fiber pulp traveling in between the first wire and the another wire; and accomplishing dewatering in a second dewatering zone of the first wire unit as pulsating dewatering with fixed dewatering lists, located on one side of the first two-wire stretch downstream of the first dewatering zone of the first wire unit and dewatering with controlled loading moveable lists which are located on a side of the first two-wire stretch which is opposite the fixed dewatering lists, the controlled loading moveable lists positioned at the gaps between the fixed dewatering lists.