Method for producing 3D fiber structures

1 . A method for producing 3D fiber structures, the method comprising:

feeding a foamed fiber furnish to an apparatus, the apparatus comprising:

a liquid-permeable substrate means having a first side and an opposing second side;

a dispenser having an outlet, wherein at least one of the dispenser and the liquid-permeable substrate means travel with respect to the other;

dispensing, by means of the dispenser, a layer of foamed fiber furnish to the first side of said liquid-permeable substrate means, so to obtain a fibrous mat, wherein the layer of foamed fiber furnish is dispensed so to comprise a predefined substantially uniform thickness, wherein the apparatus further comprises at least a reservoir to facilitate an initial natural dewatering of the fibrous mat for a first period of time and a first vacuum unit associated with the second side of the liquid-permeable substrate means so to collect fluid discharge from the dispensed layer of fibrous mat;

collecting by means of said reservoir fluid discharge for said first period of time based on at least the thickness of the layer;

applying, after the step of collecting, at least a first and a second dewatering pressure to at least a part of the second side of said liquid-permeable substrate means

wherein the liquid-permeable substrate means travels in a first direction along a length defined by a first and a second portion, wherein the dispenser is arranged to be above the first side of the liquid-permeable substrate means in said first portion,

wherein the reservoir is arranged in said first portion, wherein the first vacuum unit and a second vacuum unit are arranged sequentially along the length in said second portion, wherein the first vacuum unit is closer to the reservoir than the second vacuum unit,

wherein the first vacuum unit is configured to: apply said first dewatering pressure, wherein the second vacuum unit is configured to apply said second dewatering pressure,

wherein the first dewatering pressure is greater than the second dewatering pressure, wherein the first dewatering pressure is applied for a second period of time, wherein the first dewatering pressure is within a range of 70 kPa-100 kPa, wherein the first period of time is 1-10 minutes, wherein the second period of time is 4-6 minutes, wherein the thickness of the layer is within a range of 1-10 cm.

2 . The method according to claim 1 , wherein the second dewatering pressure is within a range of 50 kPa-80 kPa.

3 . The method according to claim 1 , wherein the method further comprises the step of, preceding the step of applying a first dewatering pressure:

applying an ultrasonic radiation towards the liquid-permeable substrate means.

4 . The method according to claim 1 , wherein the method is performed in a continuous process.

5 . The method according to claim 1 , wherein the foamed fiber furnish comprises a fiber consistency in a range of 0.5-10% based on a dry weight of the fibers, wherein the foamed fiber furnish comprises a total concentration of foaming agents in a range of 0.05-2 g/l, wherein the foamed fiber furnish comprises an air content in a range of 55-70% by volume, wherein the foamed fiber furnish is generated from a pulp slurry.

6 . An apparatus for producing 3D fiber structures, the apparatus comprising:

a liquid-permeable substrate means having a first side and an opposing second side;

a dispenser having an outlet, wherein at least one of the dispenser and the liquid-permeable substrate means travel with respect to the other;

a reservoir;

at least a first vacuum unit;

wherein the apparatus is configured to perform the method in accordance with claim 1 .