Steam treating printed fibrous sheet material

1. A printed fibrous sheet material steam treatment apparatus, comprising:

a casing defining at least one steam-treatment chamber and having at least one inlet port, configured for enabling introduction of a fibrous sheet material into the treatment chamber, and at least one outlet port configured for enabling the treated fibrous sheet material to exit from the treatment chamber;

at least one conveyor configured to contactingly receive the fibrous sheet material and convey the material into the treatment chamber through the inlet port, the conveyor being positioned with respect to the inlet port so as to constantly present a first conveyor portion disposed outside the treatment chamber and a second conveyor portion extending inside the treatment chamber; and

wherein the conveyor includes at least one absorbing surface arranged to contact the fibrous sheet material as placed on the conveyor, the absorbing surface being configured to capture condensate water.

2. The steam treatment apparatus of claim 1 , wherein the conveyor has an active surface arranged to contactingly receive the fibrous sheet material and which extends along a closed path; and

wherein the absorbing surface comprises at least one continuous absorbing layer extending along all the closed path of the active surface of the conveyor.

3. The steam treatment apparatus of claim 2 , wherein the conveyor comprises a conveying belt or a conveying drum.

4. The steam treatment apparatus of claim 1 , wherein at least the absorbing surface of the conveyor comprises a fibrous material having a dry specific weight less than 1 kg/m 2 per 1 mm of thickness, as measured in a standard environment at a temperature of 288.15 K (15° C.), pressure of 101.325 kPa (1 atm), and humidity of 0.00.

5. The steam treatment apparatus of claim 1 , wherein the absorbing surface has a water absorption capacity greater than 25%, by weight, of a dry weight of the absorbing surface, per unit volume.

6. The steam treatment apparatus of claim 1 , wherein each 0.5 cm 3 of volume of the absorbing surface defines a plurality of recesses in the form of at least one of pores, channels extending through an entire thickness of the absorbing surface, and interstices extending only partially through a thickness of the absorbing surface, and wherein a plurality of said recesses are open on an exposed surface of said absorbing surface.

7. The steam treatment apparatus of claim 6 , wherein the surface comprises hydrophilic material.

8. The steam treatment apparatus of claim 1 , wherein the conveyor comprises a conveyor belt engaged as a closed loop about at least a first idler roll outside the treatment chamber and a second idler roll inside the treatment chamber, the conveyor belt comprising at least one upper belt section extending between the first and second idler rolls and arranged to contact and convey the fibrous sheet material into the treatment chamber, and at least one lower belt section.

9. The steam treatment apparatus of claim 8 , wherein the first and second idler rolls are configured to rotate about respective horizontal axes parallel to each other and placed at different heights, wherein the rotation axis of first idler roll is lower than the rotation axis of the second idler roll, such that the upper belt section is inclined at an angle of more than five degrees with respect to a horizontal plane, and wherein a longitudinal extent of the second portion of the conveyor, measured parallel to an advancement direction of the conveyor, is greater than a longitudinal extent of the first portion of the conveyor.

10. The steam treatment apparatus of claim 1 , comprising at least one material guide disposed inside the treatment chamber and configured to receive the fibrous sheet material from the conveyor and to guide the fibrous sheet material along an operative path inside the treatment chamber, from proximate the conveyor to the outlet port.

11. The steam treatment apparatus of claim 1 , wherein the guide comprises:

a fibrous sheet material collector configured to arrange the fibrous sheet material entering treatment chamber into one or more bends;

a fibrous sheet material mover downstream of the collector along a predetermined operative path of the fibrous sheet material, the mover configured to receive and advance the bends of sheet material along a predetermined direction; and

a discharger configured to receive fibrous sheet material exiting the mover and to guide the fibrous sheet material out of the casing through the outlet port.

12. The steam treatment apparatus of claim 1 , comprising at least one steam generator configured to generate and supply steam to the treatment chamber;

wherein the steam generator is configured to generate saturated steam and to maintain inside the treatment chamber a temperature between 100 and 130° C., and to maintain inside the treatment chamber an absolute pressure between 1 and 1.7 bar.

13. A method of fixing ink on a fibrous sheet material having at least one printed side, comprising:

conveying printed fibrous sheet material into a steam-treatment chamber on a conveyor having an absorbing surface, the printed fibrous sheet material carrying an ink;

steam fixing the ink to the fibrous sheet material in the steam-treatment chamber, by guiding the fibrous sheet material along a predetermined operative path between an inlet port and an outlet port of the chamber, thereby treating the fibrous sheet material; and

extracting the treated fibrous sheet material from the outlet port;

wherein the method includes pre-humidifying the fibrous sheet material outside the steam-treatment chamber, by:

bringing the fibrous sheet material into contact with the absorbing surface of the conveyor, the absorbing surface containing condensate water; and

transferring into the fibrous sheet material at least a portion of the condensate water from the absorbing surface.

14. The method of claim 13 , wherein the conveyor contactingly receives and conveys the fibrous sheet material into the steam-treatment chamber through the inlet port, while constantly presenting a first conveyor portion disposed outside the treatment chamber and a second conveyor portion extending into the treatment chamber; and

wherein during the pre-humidifying:

the fibrous sheet material is brought into contact with the absorbing surface of the first conveyor portion; and

the portion of condensate water is transferred into the fibrous sheet material while the fibrous sheet material is conveyed by the conveyor.

15. The method of claim 13 , wherein consecutive parts of the absorbing surface are cyclically made to:

move into the treatment chamber, where an environment of saturated steam penetrates the surface portion;

move out of the treatment chamber, where water condenses to form liquid water contained within the absorbing surface; and to

contact the fibrous sheet material and transfer at least a portion of the condensed water from inside the absorbing surface to the fibrous sheet material.

16. The method of claim 13 , wherein the fibrous sheet material has two main opposite sides and is printed on only one of said sides, such that the fibrous sheet material has an unprinted side placed in direct contact with the absorbing surface.

17. The method of claim 13 , wherein steam fixing comprises:

introducing steam into the treatment chamber, including controlling introduction of steam into the treatment chamber to maintain:

a temperature between 100 and 130° C., and

an absolute pressure between 1 and 1.7 bar.

18. The method of claim 13 , wherein steam fixing comprises:

receiving pre-humidified fibrous sheet material into the treatment chamber;

withdrawing the received fibrous sheet material by a material collector;

delivering, by the collector, the withdrawn fibrous sheet material to a mover that guides the sheet material along the predetermined operative path; and

withdrawing the fibrous sheet material from the mover by a discharger that guides the treated fibrous material from the treatment chamber through the outlet port.