GB1592363A - Manufacture of constructional elements - Google Patents

Description

(54) IMPROVEMENTS RELATING TO THE MANUFACTURE OF CONSTRUCTIONAL ELEMENTS (71) We, TARMAC LIMITED, a British Company of P.O. Box 8, Ettingshall, Wolverhampton, West Midlands, do hereby declare this invention, for which we pray that a Patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to a method of manufacturing a constructional element for building purposes.

The method was especially devised for manufacture using glass fibre reinforced cement (grc) but is applicable for use with any settable construction material. The settable construction material may be cementitious material with a metal or polymer reinforcement for example or may be a thermoplastics material, with or without reinforcement, capable of being poured or sprayed in a flowable or liquid state and being settable to a solid material. It will be appreciated that the finished constructional element will have a strength dependent upon the materials from which it is made.

In the following Specification, reference will be made to a "settable constructional material" which should be taken to mean a constructional material of the type referred to in the preceding paragraph.

It is an object of the invention to provide a new or improved method of making a constructional element.

According to the invention, there is provided a method of making a constructional element comprising forming a first skin of settable constructional material, positioning thereon a plurality of first formers and depositing a layer of settable constructional material thereon, positioning on said layer a plurality of second formers, at least some of which mterpenetrate spaces between at least some of the first formers, and forming a second skin of settable constructional material thereon.

The formers may be identical or may be of different shapes. In one embodiment the formers are elongate members of generally triangular cross-section. In another embodiment individual pyramid or tetrahedral shapes may be used.

Subsequent formers may be positioned either before or after the formation of the second skin and, if positioned after the second skin, a further skin may be added.

The subsequent formers may be provided in interfitting layers separated by a further layer of settable constructional material in the same way as the first and second formers.

The formers may be removed after setting of the settable constructional material or may be left in situ.

The formers may be inflatable for use during manufacture of the constructional element and may subsequently be deflated to enable them to be removed from the finished constructional element after setting.

The invention also provides a constructional element when made by the methods set out above.

In such an element, the settable constructional material may be glass fibre reinforced cement. The formers may be of foamed synthetic plastics material or alternatively may be inflatable. Further examples of formers include rigid cores which may be withdrawable, formers of meltable materials such as alloys, wax or polymers with low melting points, or formers of granular materials. The invention will now be described in more detail by way of example only with reference to - the accompanying drawings showing a panel embodying the invention, in which drawings: FIGURE 1 is an isometric view of the panel.

FIGURE 2 is part sectional view of the panel.

Referring firstly to Figure 1 of the drawings, there is shown a panel generally indicated at -10 comprising a first skin 11 of glass fibre reinforced cement (grc) which is formed by any suitable method, for example by spraying a mixture of a cement slurry and alkali-resistant chopped glass fibre onto a suitable substrate.

A first plurality of formers 12 are then placed on the first skin 11, each former being of generally truncated triangular or trapezoidal cross-section and the formers being disposed side by side in parallel along substantially the entire length of the skin 11.

A further layer 15 of grc is deposited on the formers which are positioned on the skin, this layer being sufficient to cover the formers without completely filling the space between them.

A plurality of second formers 13 of the same cross-sectional shape as the first formers 12 are then positioned on the layer 15 of grc just formed so that they interpenetrate the spaces between the formers 12.

It is preferred that the formers 13 are placed while the supporting layer 15 of grc is still in a wet uncured state, to ensure that the grc material at the interfaces between layers is substantially homogeneous.

Finally, a second skin 14 of grc is formed on top of the second formers 13, so that all these formers are trapped between a pair of skins 11 and 13.

Although the edges of the panel are shown open in Figure 1, the two skins 11 and 14 may be made to meet at the edge.

In the drawings, it will be seen that the layer 15 of grc which separates the first and second sets of formers 12 and 13 will provide, on setting, a triangulated "skeleton" of grc within which the formers are disposed.

The configuration is shown in more detail in Figure 2 where it will be seen that the thickness of the grc layer at 16 is greater than either the first skin 11 or the intermediate layer 15 since it has been provided by two successive quantities of grc being deposited. A similar thickened portion 17 exists below the second skin 14. A flattening of the formers 12 and 13 at 18 and 19 respectively enables them to be fitted in the pattern shown leaving the thickened portions 16 and 17.

The layer 15 effectively forms reinforced cement ribs between the two skins of the panel, securely supported by the thickened portions 16 and 17, and the cross-section of the panel has a structure similar to a triangulated girder.

In the embodiment shown, the formers 12 and 13 are formed from foamed synthetic plastics material which is light in weight and has good thermal insulating properties. Since the formers can be completely encapsulated, a relatively lightweight panel can be formed which is entirely faced with fire-resistant grc and which has an insulating core. Such a panel would be suitable for internal partitions in a building in either the horizontal or vertical plane.

The strength of the panel shown would tend to be developed mostly in a direction along the length of the formers. In order to develop equal strength and rigidity in both this and the perpendicular direction in the plane of the panel, a further pair of layers of formers can be incorporated in the panel, aligned parallel with each other but transversely across the axes of the formers 12 and 13.

The subsequent formers can be positioned above the skin 14 and a further skin can be added after being placed in position, or alternatively, a first plurality of transverse formers can be placed in position immediately after the formers 13 followed by a second intermediate layer of grc to cover the profile of the formers, followed by the second transverse set of formers, followed by a final skin. This construction omits the skin 14.

It is possible to make the upper and lower skins of the panel generally flat or otherwise formed and it should for example, be possible to form constructional elements comprising sections of spheres or cylinders using the technique outlined.

The formers need not be of a rigid material but could be inflatable rubber or plastics skins which would be inflated during the formation of the panel and subsequently deflated and removed. Other types of inserts may be provided and these may be made removable after the setting of the grc layers. For example, the inserts may be of foamed plastic which could be chemically dissolved out, melted out or withdrawn longitudinally. If necessary, suitable release coatings would be applied to the formers to prevent them from bonding too intimately to the cement. Alternative materials which can be used for formers are waxes or low melting point alloys which can be melted out or granular materials loosely bound to provide formers and capable of being disintegrated by vibration or by compressed air blast for example so as to be removable from the panel after setting of the grc.

In a further embodiment, not illustrated, instead of elongate formers being used, a layer of tetrahedra or pyramids for example are placed on the lower skin, covered with an intermediate layer of grc and then a further layer of pyramidal or tetrahedal formers can be positioned in an inverted condition in the intermediate spaces. When the final skin has been added, the interior of such a constructional element would effectively be a closed cell structure having the cores as the centres of the cells and the surrounding walls being made of the grc intermediate layer.

Uses to which panels or other structural elements embodying the invention may be put are for example internal partioning as referred to above, flooring, roofing, cladding external walls, formwork and so on as permitted by the strength of the particular structural element formed and the required loading. It will be seen that removal of some or all of the formers where these are provided longitudinally within the panel will provide conduit spaces for the services provided to the building. Another possible application of panels or other constructional elements is to fill the spaces previously occupied by the formers with sound attenuating material, for example water.

Applications for the structural elements may be such as to utilise the high strengthto-weight and stiffness-to-weight ratios obtainable by the use of the invention.

If desired, the formation of the outer skins 11 and 14 can be controlled by a mould or plate for example to ensure the surface characteristics required. If inflatable formers are used, the pressure can be increased inside the formers to urge partly set material forming the upper skin against a plate or mould during curing.

Although the invention has been described in detail with reference to the formation of panels from grc, it can also be applied to the formation of panels or other constructional elements from settable constructional materials other than grc, for example cementitious materials having a homogeneous metal or polymer reinforcement dispersed therein or reinforced plastics materials capable of being used in the method of the invention.

WHAT WE CLAIM IS: 1. A method of making a constructional element comprising forming a first skin of settable constructional material, positioning thereon a plurality of first formers and depositing a layer of settable constructional material thereon, positioning on said layer a plurality of second formers, at least some of which interpenetrate spaces between at least some of the first formers, and forming a second skin of settable constructional material thereon.

2. A method according to Claim 1 wherein subsequent formers are provided in interfitting layers separated by a further layer of settable constructional material in the same way as the first and second formers.

3. A method according to Claim 2 wherein the subsequent formers are provided before the formation of the second skin.

4. A method according to Claim 2 wherin the subsequent formers are positioned after the formation of the second skin and a further skin is added after the subsequent formers have been provided.

5. A method according to any preceding claim wherein some or all of the formers are removed after setting of the settable constructional material.

6. A method according to any one of Claims 1 to 4 wherein the formers are left in situ after setting of the settable constructional material.

7. A method according to Claim 6 wherein the formers are inflatable and are inflated in use and subsequently deflated to enable them to be removed from the finished constructional element after setting.

8. A constructional element when made by the method according to any one of

Claims (1)

1. Claims 1 to 7.

   9. A constructional element according to Claim 8 wherein the settable constructional material is glass fibre reinforced cement.

   10. A constructional element according to Claim 8 or Claim 9 wherein the formers are of foamed synthetic plastics maferial.

   11. A constructional element according to Claim 8 or Claim 9 wherein the formers are inflatable.

   12. A constructional element according to any one of Claims 8 to 11 adapted to have the formers removed therefrom.

   13. A constructional element according to any one of Claims 8 to 12 wherein the formers are elongate members.

   14. A constructional element according to Claim 13 wherein the formers are of generally triangular cross-section.

   15. A constructional element according to any one of Claims 8 to 12 wherein the formers are a plurality of individual pyramids or tetrahedra.

   16. A method of making a constructional element substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

   17. A constructional element substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.