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Patent Searching and Data


Title:
MANUFACTURE OF CELLULAR MATERIAL
Document Type and Number:
WIPO Patent Application WO/2002/032602
Kind Code:
A2
Abstract:
The invention provides a method of making a porous material, wherein a web of open textured woven or knitted textile fabric (10) is unwound from a reel (12) and fed through an open topped vessel (14) which contains a cementitious mix (16). A roller (18) in the vessel ensures that the fabric (10) spends sufficient time in the mix to be thoroughly impregnated by the mix. The mix accordingly fills the openings in the weave or knit of the fabric (10). A slit like air nozzle (20) is located close to where the impregnated fabric emerges from the vessel (14). Air pressure, and the linear speed at which the fabric (10) is travelling, determines how much of the cementitious material in the openings is blown out and falls back into the vessel (14). To assist the air jet in removing mix from the openings, the fabric (10) can be vibrated.

Inventors:
HOURAHANE DONALD HENRY (ZA)
Application Number:
PCT/ZA2001/000122
Publication Date:
April 25, 2002
Filing Date:
August 23, 2001
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
HOURAHANE DONALD HENRY (ZA)
International Classes:
B28B1/00; B28B19/00; B28B23/00; (IPC1-7): B23B13/00
Domestic Patent References:
WO1997026395A11997-07-24
Foreign References:
DE3341595A11985-05-02
EP0990626A12000-04-05
Attorney, Agent or Firm:
Bacon, Brian (Brian Bacon & Associates 2nd Floor Mariendahl House Fedsure on Main 7700 Newlands, ZA)
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Claims:
CLAIMS :
1. A method of manufacturing a cellular material which comprises impregnating a fabric of the kind defined with a cementitious mix, openings in the knit or weave being free of mix thereby to leave passageways which pass through the fabric.
2. A method as claimed in claim 1, wherein the cementitious mix is sprayed onto the fabric to impregnate it.
3. A method as claimed in claim 1, wherein the fabric is dipped into the cementitious mix to impregnate it,.
4. A method as claimed in claim 2 or 3 and including the step of blowing air against the impregnated fabric to remove cementitious mix from the fabric and unblock openings that were filled with mix during impregnation.
5. A method as claimed in claim 2 or 3 and including the step of leaving the fabric unsupported after impregnation so that cementitious mix falls from openings in the weave or knit and unblocks these openings.
6. A method as claimed in any one of claims 1 to 5 and including the step of vibrating the fabric to promote removal of excess mix from said openings.
7. A method as claimed in claim 4, wherein the impregnated fabric is fed past an air nozzle which is in the form of a slit, the slit being elongate in the direction transverse to the direction in which the fabric is moving.
8. A method as claimed in claim 7 and including adjusting the width of the slit to vary the airflow.
9. A method as claimed in any one of claims 1 to 8, wherein the fabric is in the form a web which is advanced and impregnated with mix whilst moving, the impregnated fabric being cut into pieces and the pieces being stacked to form layers before the mix sets whereby the layers bond to one another in the stack.
10. A method as claimed in any one of claims 1 to 8, wherein the fabric is in the form a web which is advanced and impregnated with cementitious mix whilst moving, the impregnated fabric being stacked by zigzag folding the fabric before the cementitious mix sets thereby to form layers which bond to one another in the stack.
11. A method as claimed in claim 9 or 10, and comprising compressing the stack to consolidate it,.
12. A method of manufacturing cellular material substantially as hereinbefore described with reference to the accompanying drawings.
13. A cellular material when made by the method claimed in any preceding claim.
14. A concrete product which comprises layers of fabric of the kind defined which are impregnated with a cementitious mix so that the concrete mix is in the interstical spaces of the yarn, there being air filled cells in the product.
15. A method of making the product claimed in claim 14, in which the fabric is impregnated with a cementitious mix, and excess mix is removed from openings in the knitted or woven fabric which are bounded by the yarn to form said cells.
16. A method of making the product claimed in claim 14 in which the fabric is impregnated with a cellular concrete mix.
Description:
MANUFACTURE OF CELLULAR MATERIAL FIELD OF THE INVENTION THIS INVENTION relates to the manufacture of cellular material.

BACKGROUND TO THE INVENTION In the specification of my PCT application PCT/US97/00362 (published as W097/26395) there is described a yarn which includes a core and a multitude of staple fibres forming a sheath which envelopes the core and provides an extended surface area and interstical spaces for infiltration by cement fines and hydrates, the staple fibres being spun around the core and having sufficient freedom of radial movement to provide said spaces and permit ingress of cement fines and the formation of its hydrates in said spaces. Such a yarn is known as a friction spun yarn.

A specific feature of the friction spun yarn of W097/26395 is that the fibres are attached to the core at intervals along the length of the core. This inhibits delamination, that is, sliding of the core with respect to the fibres, The specification of my PCT application PCT/US97/00362 is hereby incorporated into the present specification.

As is explained in specification W097/26395, a cementitious mix bonds to a fabric woven or knitted using yarn of the type described above. The resultant product is becoming known in the art as textile concrete which is a cementitious material with one or more textile layers incorporated in it.

A fabric knitted or woven using a friction spun yarn comprising a core and a sheath of staple fibres which envelopes the core will hereinafter be referred to as a fabric of the kind defined.

BRIEF DESCRIPTION OF THE INVENTION According to one aspect of the present invention there is provided a method of manufacturing cellular material which comprises impregnating a fabric of the kind defined with a cementitious mix, the openings in the knit or weave being free of mix thereby to leave passageways which pass through the fabric.

The cementitious mix can be sprayed onto the fabric or the fabric can be dipped into the mix. If the mix is sprayed onto the fabric and the quantity of mix sprayed is controlled, said openings remain free of mix whilst the interstices of the sheaths of the yarn are fitted. However, if the openings fill with mix during spraying, or the mix is applied by dipping the fabric in a bath of the mix, the mix which blocks the openings can be removed by blowing air against the fabric or by leaving it unsupported so that the mix falls from the openings in the weave or knit. The fabric can be vibrated to promote removal of excess mix.

The impregnated fabric can be fed past an air nozzle which is in the form of a slit, the slit being elongate in the direction transverse to the direction in which the fabric is moving. The width of the slit can be adjustable to enable air flow to be varied.

In the preferred form the fabric is in the form a web which is advanced and impregnated with mix whilst moving, the impregnated fabric being cut into pieces and the pieces stacked to form layers, or stacked by zig-zag folding the fabric before the mix sets thereby to form layers whereby the layers bond to one another in the stack.

The stack can be compressed to consolidate it.

According to a further aspect of the present invention there is provided a concrete product which comprises layers of fabric of the kind defined which are impregnated with a cementitious mix so that the concrete mix is in the interstical spaces of the yarn, there being air filled cells in the product.

To form the product the fabric can be impregnated with a cementitious mix, and excess mix can be removed from openings in the knitted or woven fabric which are bounded by the yarn to form said cells. Alternatively the fabric can be impregnated with cellular concrete mix.

BRIEF DESCRIPTION OF THE DRAWINGS For a better understanding of the present invention, and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying drawings in which :- Figure 1 diagrammatically illustrates a method of manufacturing a cellular material in the form of a tile ; and Figures 2 and 3 illustrate weave patterns.

DETAILED DESCRIPTION OF THE DRAWINGS Referring firstly to Figure 1, a web of open textured woven or knitted textile fabric 10 of the kind defined is unwound from a reel 12 and fed through an open topped vessel 14 which contains a cementitious mix 16. A roller 18 in the vessel ensures that the fabric spends sufficient time in the mix to be thoroughly impregnated by the mix, The interaction between the cementitious mix and the sheath of the yarn is described in PCT specification W097/26395 and will not be repeated here, The mix also fills the openings in the weave or knit of the fabric. It will be understood that the size and the number of openings in any given area depends on the tightness of the weave or knit. The adjacent strands of the fabric do not have to be evenly spaced.

Thus there can be a number of strands which are close together, then an opening where the strands are more widely spaced, and then another group of strands, The openings in the fabric can be rectangular (including square), hexagonal etc.

A slit like air nozzle 20 is located close to where the impregnated fabric emerges from the vessel 14. The nozzle is elongate in the horizontal direction, that is, in a direction transverse to the direction in which the fabric 10 is moving. The nozzle extends the full width of the fabric. Air pressure, and the linear speed at which the fabric is travelling, determines how much of the cementitious material in the openings is blown out and falls back into the vessel. To assist the air jet in removing mix from the openings, the fabric can be vibrated. In some instances leaving the fabric unsupported and vibrating it without the use of a jet of air is sufficient to remove surplus mix.

The fabric, prior to the mix setting, is cut into pieces and the pieces stacked. Alternately, the fabric web can be zig-zag folded and stacked. This, however, produces areas of increased thickness along the edges of the stack which could be undesirable for certain applications. The stack can be compressed before the mix sets.

This can be achieved by passing the stack through a pair of pressure rollers or placing it between the platens of a press. In Figure 1 it is this latter form which is illustrated, the platens being shown at 22.

The resultant sheets are, because of their cellular construction, perforated and are mainly intended for sound attenuation, sound being allowed to pass through the perforations. Where the method is used to produce ceiling tiles, the sound can be absorbed by an appropriate open textured sound absorbing material in the air space above the tiles. In some cases the air space above the tiles will suffice without sound absorbing material.

The weave of Figure 2 is suitable for use in making tiles. When the pieces are stacked the weave openings form random patterns some of which are in the form of tortuous passages which pass through the tiles If made using gypsum plaster, the perforated sheets have an appropriate finish for use as a ceiling tile. These are typically 600mm square and located in a support frame. Perforated tiles made as described above are self supporting and capable of supporting sound absorbing material over the 600mm x 600mm area of the tile. The term cementitious mix as used herein is intended to be broad enough to cover products such as gypsum plaster which set to form an hydraulic matrix.

If required the woven or knitted fabric can incorporate glass or other reinforcing strands at appropriate centre distances to create a rigid frame around the perforated area of the tile, The perforated tile and its reinforcing frame can be made in an in-line operation, the required reinforcing being pre-woven or knitted into the textile fabric.

Perforated sheets made as described can be assembled to create thick panels that allow the wind to pass through thus minimising wind load on their support system. Such sheets also find application along highways for sound attenuation purposes.

Another possible application is the creation of flat porous surfaces over angle grooved drainage plates for use around swimming pools, or as the upper surface of marine or marina platforms, to provide a non-slip surface, In areas prone to freezing the perforated plates could incorporate low voltage electric heating to prevent the formation of ice. This concept is particularly useful on the tread area of steps. The heating wires can be included in the fabric during weaving or knitting.

Other possible uses are in desalination and for humidifying purposes.

Porous panels of the type produced by the procedure described can be arranged vertically and sea water can be allowed to trickle down over the panels from a header tank. Air can be blown through the pores in the panels, or allowed to blow through, the air picking up water vapour as it passes through. If there is a growing tunnel on the downstream side of the panel, the water vapour can be allowed to condense out thereby to provide a water supply for the produce growing in the tunnel. The moisture laden air can be used to humidify any space downstream of the panel.

If the openings in the impregnated fabric layers are randomly distributed in the finished product (as happens with the weave of Figure 2), the effect is to produce a hard material which simulates coral, However, the impregnated layers can have the openings in them aligned thus producing passageways which pass through the block or tile produced by stacking a number of impregnated fabric layers. To assist in obtaining this alignment the impregnated layers can be stacked onto a plate with upwardly protruding fingers. These pass through the stack. The open weave of Figure 3 can be used for this purpose. The openings 24 can have a foamed material such as polystyrene or other material in them. The polystyrene constitutes the aligning fingers and is left in place. A"tile"produced using a weave such as that in Figure 2 can in certain applications be used to close-off the openings 24 at one or both ends, In another form groups of carbon or Kevlar weft threads are provided at equal intervals along the length of the fabric web. The fabric web, after impregnation, is zig-zag folded with the carbon or Kevlar threads at alternate folds, By this means it is possible to create a lightweight beam with Kevlar or carbon threads in the tension surface of the beam.

Another method of making a fabric reinforced cellular material comprises stacking a number of layers of fabric of the kind defined in a mould. Cellular concrete in liquid form is then poured into the mould to infiltrate the fabric layers. The liquid concrete also infiltrates the spaces within the sheaths of the friction spun yarns of the layers of fabric.

Cellular concrete mixes are well known in the art. A hydrolyse protein or a gelatine such as is used in the wine industry for"fining"is thoroughly mixed with water and dry cementitious powder to form a milky slurry that can be poured. Conventionally this mix is allowed to set in moulds to form blocks of lightweight cellular concrete, In accordance with the present invention, however, it is poured into a mould containing fabric as described above.

Sheets manufactured as described in corrugated form can be stacked with the corrugation of adjacent sheets at right angles to one another. This results in air passageways throughout the entire stack through which air blows regardless of wind direction. The stack can be used to treat waste water. The water is dribbled onto the top of the stack so that it filters down through the pores of the stack. Aerobic digestion of the solid waste takes place as the water percolates through each sheet in turn.