INSTALLATION FOR DRYING A DAMP NON-WOVEN WEB

Abstract

An installation for drying a non-woven web includes a device (10, 11), a diffusion chamber (10) having an outlet fitting (21) in which there is mounted a perforated sheet (24) creating a drop in pressure.

Claims

1. An installation for drying a non-woven web which comprises: a fan (6) with a delivery and an intake, a heating oven (3) having an inlet and an outlet, an inlet conduit (C1) which has a branch and which connects the delivery of the fan (6) with the inlet of the oven (3) and sends delivered air to the inlet of the oven, a heat source (4) arranged in such a way that the air delivered in the inlet conduit (C1} is heated, an outlet conduit (C2) which connects the outlet of the oven (3) with the intake of the fan (6), a branch conduit (C3), in the branch of the inlet conduit (C1) upstream of the heat source (4), connecting the inlet conduit (C1) with an inlet of a drying device (10, 11), a means of transport (2) which displaces a web in the drying device (10, 11) and in the oven (3), the drying device (10, 11) being upstream of the oven (3) in the direction of displacement of the web, a conduit (C4) for extracting the air from the drying device (10, 11), wherein the drying device comprises a diffusion chamber (10) having an outlet fitting (21) in which there is mounted a perforated sheet (24) with perforations, wherein downstream of the first perforated sheet (24) is mounted in the outlet fitting (21) or in a channel which is clamped to the fitting (21) a honeycombed bundle (28), the dimension of whose cells is greater than that of the perforations of the perforated sheet (24).

2. An installation according to claim 1, wherein the bundle (28) is supported by another perforated sheet (29) having a void rate that is greater than 40% to 60%.

3. An installation according to claim 1, wherein the bundle (28) is mounted in a movable drawer (31).

4. An installation according to claim 1, wherein the ratio of length of the bundle to equivalent diameter of the bundle is higher than 10.

5. An installation according to claim 1, characterised in that the perforated sheet (24) has a void rate between 10% and 60%.

6. An installation according to claim 1, characterised in that the perforated sheet (24) is mounted in a movable drawer (22) which has a handle (23) outside the fitting (21}.

7. An installation according to claim 1, characterised in that the void rate of the perforated sheet (24) ranges from 40 to 60% from a side of the inlet of the diffusion chamber (10) to 10 to 20% at the place where the void rate is greatest.

8. An installation according to claim 1, characterised in that the perforated sheet (24) is covered with a thin metallic cloth (30) having a void rate between 25% and 50%.

9. An installation according to claim 8, wherein a dimension of the perforation of the cloth are from 0.1 mm to 1 mm.

10. An installation according to claim 1, characterised in that the bundle (28) is mounted in a movable drawer (31).

11. The installation of claim 1, wherein the perforated sheet has perforations with a dimension from 2 to 8 mm.

12. The installation of claim 8, wherein the cloth has perforations with a dimension from 0.5 to 2 mm and the perforated sheet has perforations with a dimension from 2 to 8 mm.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In the attached drawings, given solely by way of example:

[0023] FIG. 1 shows the installation in accordance with the invention;

[0024] FIG. 2 is a perspective view of the diffusion box;

[0025] FIG. 3 is a side elevation;

[0026] FIG. 4 is a perspective view of the perforated sheet; and

[0027] FIG. 5 is a perspective view of another diffusion box.

PREFERRED EMBODIMENTS FOR CARRYING OUT THE INVENTION

[0028] In FIG. 1, the dried web 1 circulates around a drum 2 or on a conveyor.

[0029] Hot air under pressure is injected through an inlet conduit C1 in the hood 3 thanks to a fan V1 6 (called main fan) and a heat source 4 which heats up the air. This heat source 4 can be, for example, a gas burner or an (oil, air, water or electrical) heat exchanger.

[0030] This hot air then passes over the damp web and the drum 2 (or the conveyor cloth): by means of this process, the water contained in the web is evaporated as the web advances on the drum 2 (or on the conveyor). The air which has passed over the web has been cooled and laden with moisture. It is then taken in by an extraction conduit C2 inside the drum 2 by means of the fan V1 6 and heated up anew by the heat source 4 and reinjected into the loop and so on.

[0031] The heat source 4 can be positioned upstream or downstream of the fan V1 6. It is preferably positioned downstream, as shown in the figure, in the case of an exchanger and upstream in the case of a gas burner.

[0032] The motor of this fan V1 6 is controlled by a frequency-variator 14.

[0033] The temperature of the hot air injected in the hood 3 is regulated by the action of the heat source 4.

[0034] A portion of the cooled and damp air is drawn off outside the loop so that the humidity is not concentrated in the circulation loop. Thus a portion of the cooled and damp air is drawn off by means of the branch conduit C3 thanks to the pressure generated by the fan V1 (6) at the outlet if this is sufficient or thanks to a supplementary branch fan V2 (8).

[0035] The branch conduit C3 can be connected upstream of V1.

[0036] Flaps 9a can be installed in the branch conduit C3 in order to be able to regulate the value of the extracted flow rate.

[0037] In the case where there is a branch fan V2 (8), the motor of this fan can be controlled by a frequency-variator. If there are regulating flaps 9, this control by means of a variator is unnecessary.

[0038] In order to make good this air deficit in the loop, reserve air is taken in in the production room upstream of the fan V1 through the reserve pipework 7.

[0039] The cooled and damp air drawn off by the branch conduit C3 is then injected into a diffusion box 10 which will diffuse the air above an intake drying box 11 which is located upstream of the oven 3 and on which the web that is to be dried circulates.

[0040] This intake drying box 11 can be located either in a conveyor (web support=cloth of conveyor) or in a cylinder (web support=nickel cylinder, perforated sheet, metallic cloth).

[0041] The air is taken in in the drying box 11 by means of a final extraction fan V3 12. This fan 12 is preferably positioned as close as possible to the drying box 11.

[0042] The diffusion box represented in FIGS. 2 and 3 consists of a parallelepipedal chamber 9 having two front faces, one of which is closed and the other of which receives the flexible coupling 13 at the inlet. A parallelepipedal fitting 21 of the same length as the chamber issues from the large lower face. The width of the chamber 9 is the same as the width of the fitting 21. The width L of the fitting 21 ranges from 400 to 1200 mm. Mounted in this fitting 21 there is a movable sliding drawer 22 having a handle 23 and bearing a first perforated sheet 24 having a void rate of 10 to 60%. The drawer 22 slides in the fitting 21 by means of slide rails 25. The first perforated sheet 24 is covered with a thin metallic cloth 30 having a void rate of 25 to 50%.

[0043] Clamped at the fitting 21, by means of clamps 26, there is a channel 27 in which there is mounted a honeycombed bundle 28 supported by a second perforated sheet 29 having a void rate of 40 to 60%. The cells of the honeycombed bundle 28 have an equivalent diameter of the circle inscribed in the hexagon of 4 to 10 mm.

[0044] FIG. 4 shows that the first perforated sheet 24 has a void-rate gradient.

[0045] In FIG. 4 the portion to the right of the first sheet has a void rate that is greater than the portion to the left. The portion to the right has a void rate of 40 to 60%. The portion to the left has a void rate of 10 to 20%. The variation in the void rate from right to left can be effected gradually or in stages. This variation can be obtained by means of the same number of perforations, but with the dimensions thereof increasing from right to left or by means of perforations having the same dimensions, but in a different number.

[0046] FIG. 5 is a view, similar to FIG. 2, of a diffusion box in which the honeycombed bundle 28 is mounted on a movable drawer 31.