GB2125751A - Porous panel - Google Patents

Abstract

A porous panel, e.g. for the distribution of a freezing point depressant liquid on an aircraft surface in order to provide protection against atmospheric icing. The porous panel comprises an outer sheet (1) of porous material over the surface of which the fluid is to be distributed, the outer sheet comprising a porous, reinforced plastic composite material, a backing sheet (13) in contact with one side of the outer sheet (1), the backing sheet comprising a porous plastic material having a pore size smaller than the pore size of the outer sheet, and a sheet of fluid impervious material (15) spaced from the backing sheet so that fluid can be introduced into the space between the backing sheet and the impervious sheet whence it can pass through the porous sheets to the outer surface of the outer sheet. A protective porous or perforated metal sheet (17) may also be bonded to the outer sheet (1). <IMAGE>

Description

SPECIFICATION Porous panel This invention relates to a porous panel for use principally, but not exclusively, for the distribution of a freezing point depressant liquid on an aircraft surface in order to provide protection against atmospheric icing.

U.K. Patent No. 724019 describes a po rous panel assembled by mechanical fasteners. A panel of the type described in that patent is shown diagrammatically in Fig. 1 of the accompanying drawings. As will be seen from that Figure, the panel comprises an outer skin 1 of porous metal, a sheet 2 of microporous plastic, edge spacers 3, and a nonporous backing sheet 4 assembled to the outer skin 1 by mechanical fasteners 5. A cavity 7 is defined between sheets 2 and 4, and a connection 6 is provided to admit liquid into the cavity 7. Modified forms of this panel are described in U.K. Patents 1094372 and 1102958.

An object of the present invention is to provide an improved porous panel.

According to the invention there is provided a porous panel for the distribution of fluid, comprising an outer sheet of porous material over the surface of which the fluid is to be distributed, the outer sheet comprising a porous, reinforced plastic composite material, a backing sheet in contact with one side of the outer sheet, the backing sheet comprising a porous plastic material having a lower porosity than the outer sheet, and a sheet of fluid impervious material spaced from the backing sheet so that fluid can be introduced into the space between the backing sheet and the impervious sheet whence it can pass through the porous sheets to the outer surface of the outer sheet.

Embodiments of the invention are described in detail below, by example only, with reference to Figs. 2 and 3 and 3a of the accompanying drawings which show embodiments of the porous panel of the invention.

The illustrated porous panels comprise an outer sheet 1 of a reinforced plastic composite material, a porous plastic backing sheet 1 3 in contact with the outer sheet 1 2 and a spaced apart impervious sheet 1 5.

The embodiment of Fig. 2 comprises an outer sheet 1 consisting of porous reinforced plastic composite material having a pore size of the order of 20 to 100 microns. This material may be produced either by impregnating reinforcing fibres (e.g. glass fibres or carbon fibres) with resin treated to produce an open cell foam, by incorporation, and controlled expansion during the curing phase, of gas or liquid bubbles or solid particles, or alternatively by controlling the quantity of resin applied so that sufficient resin is available to bond the fibres together without com pletely filling the spaces between them.

The backing layer 1 3 is of similar material, but with a fibre content which is either zero or at least less than the fibre content of the outer layer 1. This permits closer control of the porosity. The layer 1 3 has a pore size of the order of 5 microns and a relatively low porosity. This enables fluid pressure to be developed behind the layer 1 3 so as to obtain an even distribution of liquid during operation.

The layer of impervious material 1 5 is spaced from the layer 1 3 to define a cavity therebetween, and this cavity is substantially filled with a material 14 having a coarse structure which permits free passage of liquid but provides a support for the layer 1 5. The layer 14 may, for example, be an open weave cloth, or a mat of coarse chopped strands with a resin content sufficient to bond the strands at their contact point but without filling the holes therebetween.

The outer surface of the outer layer 1 is preferably and advantageously covered with a thin sheet of porous or perforated metal 1 7 which is bonded thereto and protects the porous panel from erosion by rain, sand and other materials. The sheet 1 7 also provides protection against lightening strikes.

The embodiment shown in Fig. 3 is identical to that shown in Fig. 2 except that the layer 1 4 is replaced by loops 1 6 which are woven into the fibre reinforcement of the outer layer 1. The loops 1 6 permit the use of a much lighter backing sheet 1 5 since this could then be supported at close intervals over the surface of the panel.

As shown schematically in Fig. 3a, mechanical fasteners 18, i.e. rivets, can be used to attach the sheet 1 5 to the outer sheet 1 to prevent the panel from opening up due to the internal pressure. A spacing of from 20 to 30 mm, for example, might be appropriate for the rivets 18.

The sheet making up the porous panel can be assembled together using rivets through the sheets at the peripheral regions of the space between the sheets. Alternatively, the sheets can be bonded together using an adhesive at the edges of the space, which adhesive may be flexible.

1. A porous panel for the distribution of fluid, comprising an outer sheet of porous material over the surface of which the fluid is to be distributed, the outer sheet comprising a porous, reinforced plastic composite material, a backing sheet in contact with one side of the outer sheet, the backing sheet comprising a porous plastic material having a lower porosity than the outer sheet, and a sheet of fluid impervious material spaced from the backing sheet so that fluid can be introduced into the space between the backing sheet and the impervious sheet whence it can pass through

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (8)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Porous panel This invention relates to a porous panel for use principally, but not exclusively, for the distribution of a freezing point depressant liquid on an aircraft surface in order to provide protection against atmospheric icing. U.K. Patent No. 724019 describes a po rous panel assembled by mechanical fasteners. A panel of the type described in that patent is shown diagrammatically in Fig. 1 of the accompanying drawings. As will be seen from that Figure, the panel comprises an outer skin 1 of porous metal, a sheet 2 of microporous plastic, edge spacers 3, and a nonporous backing sheet 4 assembled to the outer skin 1 by mechanical fasteners 5. A cavity 7 is defined between sheets 2 and 4, and a connection 6 is provided to admit liquid into the cavity 7. Modified forms of this panel are described in U.K. Patents 1094372 and 1102958. An object of the present invention is to provide an improved porous panel. According to the invention there is provided a porous panel for the distribution of fluid, comprising an outer sheet of porous material over the surface of which the fluid is to be distributed, the outer sheet comprising a porous, reinforced plastic composite material, a backing sheet in contact with one side of the outer sheet, the backing sheet comprising a porous plastic material having a lower porosity than the outer sheet, and a sheet of fluid impervious material spaced from the backing sheet so that fluid can be introduced into the space between the backing sheet and the impervious sheet whence it can pass through the porous sheets to the outer surface of the outer sheet. Embodiments of the invention are described in detail below, by example only, with reference to Figs. 2 and 3 and 3a of the accompanying drawings which show embodiments of the porous panel of the invention. The illustrated porous panels comprise an outer sheet 1 of a reinforced plastic composite material, a porous plastic backing sheet 1 3 in contact with the outer sheet 1 2 and a spaced apart impervious sheet 1 5. The embodiment of Fig. 2 comprises an outer sheet 1 consisting of porous reinforced plastic composite material having a pore size of the order of 20 to 100 microns. This material may be produced either by impregnating reinforcing fibres (e.g. glass fibres or carbon fibres) with resin treated to produce an open cell foam, by incorporation, and controlled expansion during the curing phase, of gas or liquid bubbles or solid particles, or alternatively by controlling the quantity of resin applied so that sufficient resin is available to bond the fibres together without com pletely filling the spaces between them. The backing layer 1 3 is of similar material, but with a fibre content which is either zero or at least less than the fibre content of the outer layer 1. This permits closer control of the porosity. The layer 1 3 has a pore size of the order of 5 microns and a relatively low porosity. This enables fluid pressure to be developed behind the layer 1 3 so as to obtain an even distribution of liquid during operation. The layer of impervious material 1 5 is spaced from the layer 1 3 to define a cavity therebetween, and this cavity is substantially filled with a material 14 having a coarse structure which permits free passage of liquid but provides a support for the layer 1 5. The layer 14 may, for example, be an open weave cloth, or a mat of coarse chopped strands with a resin content sufficient to bond the strands at their contact point but without filling the holes therebetween. The outer surface of the outer layer 1 is preferably and advantageously covered with a thin sheet of porous or perforated metal 1 7 which is bonded thereto and protects the porous panel from erosion by rain, sand and other materials. The sheet 1 7 also provides protection against lightening strikes. The embodiment shown in Fig. 3 is identical to that shown in Fig. 2 except that the layer 1 4 is replaced by loops 1 6 which are woven into the fibre reinforcement of the outer layer 1. The loops 1 6 permit the use of a much lighter backing sheet 1 5 since this could then be supported at close intervals over the surface of the panel. As shown schematically in Fig. 3a, mechanical fasteners 18, i.e. rivets, can be used to attach the sheet 1 5 to the outer sheet 1 to prevent the panel from opening up due to the internal pressure. A spacing of from 20 to 30 mm, for example, might be appropriate for the rivets 18. The sheet making up the porous panel can be assembled together using rivets through the sheets at the peripheral regions of the space between the sheets. Alternatively, the sheets can be bonded together using an adhesive at the edges of the space, which adhesive may be flexible. CLAIMS

1. A porous panel for the distribution of fluid, comprising an outer sheet of porous material over the surface of which the fluid is to be distributed, the outer sheet comprising a porous, reinforced plastic composite material, a backing sheet in contact with one side of the outer sheet, the backing sheet comprising a porous plastic material having a lower porosity than the outer sheet, and a sheet of fluid impervious material spaced from the backing sheet so that fluid can be introduced into the space between the backing sheet and the impervious sheet whence it can pass through the porous sheets to the outer surface of the outer sheet.

2. A panel according to claim 1, wherein the outer sheet comprises reinforcing fibres impregnated with a treated resin.

3. A panel according to claim 1 or 2, wherein the said space is substantially filled with a material having a coarse structure which permits free passage of fluid but provides a support for the impervious sheet.

4. A panel according to claim 1 or 2, wherein loops woven into the outer sheet extend into the said space and support the impervious sheet.

5. A panel according to any preceding claim, wherein the panel is prevented from opening up due to internal pressure by mechanical fasteners connecting the outer and impervious sheets.

6. A panel according to any preceding claim, wherein a sheet of porous or perforated metal is bonded to the outer surface of the outer sheet as a protective covering.

7. A panel according to any preceding claim, wherein the porous sheets and the impervious sheet are assembled by adhesive bonding.

8. A porous panel substantially as herein described with reference to Fig. 2 or 3 of the accompanying drawings, with or without the modificaton of Fig. 3a.