GB1571898A - Manufacture of shaped objects - Google Patents

Description

(54) IMPROVEMENTS IN OR RELATING TO THE MANUFACTURE OF SHAPED OBJECTS (71) We, EuRoc DEVELOPMENT AB, a Swedish Company, of Stormgatan 14, 211 20 Malmö, Sweden, do hereby declare the 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: The present invention relates to a method of moulding an object from a setting material such as to provide said object with opposite sides of a given configuration.

In the manufacture of building elements it is known to spray a fibre-reinforced binding material, such as a cement-water mixture containing glass fibres, on to a moulding surface. The moulding surface may be planar, of single curvature, or of multi-curvature. Normally, a satisfactory surface finish can be obtained on the side of the product facing the moulding surface, provided that the surfaces of the mould and the shaped surface of the product exhibit suitable release or parting characteristics. In order to obtain a high-grade homogeneous product, however, it may be preferred to subject the moulding material to further treatment. In this respect, the moulding material may be treated during the spraying operation or immediately thereafter.For example, any air-pores present in the sprayed material may be removed by sub iecting the material to a partial vacuum, or by applying pressure to the material, such as by compressing the material lying against the mould by means of a roller. When applying such techniques, however, it is normally not possible to provide a good surface finish on the surfaces of the material facing the nozzle of the spraying apparatus. Immediately after the spraying operation, this surface is uneven and undulated. When the material is pressed, it is not possible for air trapped in the surface irregularities to escape therefrom and the air will remain in the surface of the material to form pores.Although in the case of a planar mould, and sometimes also in the case of a mould of but single curvature, air inclusions can be removed from the moulding material by compressing the material by means of a roller and optionally vibrating the binding material at the same time as the material is sprayed onto the mould; this requires the properties of the binding material to be such that the material will not stick to - and be lifted up by the roller.

In accordance with one known technique, the sprayed binding material may be pressed, vibrated and smoothed with a steel plate in simple method steps. It is possible in this way to obtain a good surface finish, although reproduceability with respect to the thickness of the sprayed, pressed and cured product is poor or totally unacceptable for certain fields of use.

It is also known to obtain a smooth and uniform surface by means of one or more knives arranged above a conveyor belt on which moulds filled with binding material sprayed thereon are advanced at uniform speeds. This method is readily effected and is satisfactory for manufacturing certain types of building elements, but has unacceptable disadvantages with regard to other types of building elements with which the main surfaces of the building elements must exhibit a particularly good surface finish and with which the thickness must lie within precise limits. When manufacturing building elements having surfaces of double curvature or some other intricate surface curvature, the desired surface finish of the building element cannot be obtained by means of this latter technique.

Although building elements produced in accordance with these known spraying techniques, and having a thickness which lacks the precision necessary for certain usages, can be used within certain other fields of use, these building elements still exhibit a multiplicity of disadvantages of varying degree of seriousness. The product must be relatively thick and heavy. It must be dimensioned according to the worst result of a production series. Thus, it is expensive to manufacture. This is of particular significance when the sprayed material is expensive or when it contains an expensive additive. Other disadvantages are those of a purely functional and aesthetic nature.

Tn the case of a sprayed binding material containing glass fibres, contact between the material and the fibres is often poor, particularly when the material contains a large quantity of fibres and the binding material has a relatively high viscosity. This problem can be solved to a certain extent, by, for example, using an aluminium roller, with which the glass fibres are rolled and pressed into more intimate contact with the binding material. It is not possible with this method, however, to obtain a high-grade product of uniform thickness and with a smooth surface and good surface finish.

This invention consists in a method of moulding an object from a setting material, such as to provide said object with two mutually opposing sides of a given configuration, said method comprising spraying a layer of said setting material onto a first support surface having the desired configuration of one of said sides, spraying a fur other layer of said setting material onto a second support surface having the desired configuration of the other of said sides, and while the setting material on the first and second support surfaces is still shapeable moving the charged first support surface towards the charged second support surface to form a mould such that the distance between said surfaces equals the desired thickness of the object, said surfaces being brought towards each other at an acute angle therebetween, so that the layers of setting material are pressed into the desired configurations progressively from one edge of each layer to the opposite edge thereof; applying a pressure to said mould to form the desired object, and removing the shaped object from said mould.

Embodiments of the invention will now be described in more detail by way of example with reference to the enclosed schematic drawing, in which: - Figure 1 is a perspective view of two mould halves for manufacturing tiles of glass fibre reinforced concrete, said mould being composed of a positive half and a negative half, Figure 2 shows the mould halves after application of precoat; Figure 3 shows the same mould halves after application of a mixture of fibres and cement; Figure 4 shows the positive and negative mould halves after having been brought together to form a mould; Figure 5 shows the tile after its removal from the mould; and Figure 6 shows a number of tiles stacked for curing purposes.

With reference to the Figures, the manufacture of tiles of reinforced concrete comprises the step of placing two support surfaces for forming mould halves 1 and 2 on a transport belt. The left one of the halves is a positive mould portion and the right one a negative mould portion. Both mould surfaces are undulated. Each mould half is covered with a vacuum-formed protective sheet 3 of thermoplastic material, also of undulating configuration, to prevent water present in the tile from evaporating therefrom and for removing the tile from the mould after curing. After application of the plastics sheets, the mould halves are transported by the belt to a station (Figure 2) where a precoat 4 is applied to the surface of the thermoplastic sheets.

The precoat preferably comprises an aqueous mixture of sand and Portland cement, said mixture also containing any required colour pigment and admixtures.

The precoat is applied by spraying a thin layer of the aqueous mixture suspended in a gaseous medium from a spray nozzle arranged above the transport belt.

The composition of the precoat mixture is as follows: Portland cement 1 part sand and 0.50 water 0.35 By "part" is meant "part by weight".

The mould halves having the precoat applied thereon are then moved to a station (Figure 3) in which a layer 5 of a mixture for the reinforcing mass of the tile is applied. The composition of this mixture is as follows: Portland cement 1 part sand 0.50 water 0.35 fibres 0.1 In the present embodiment the fibre material comprises strands of alkali resistant glass fibre having a diameter of 12am, each strand containing 200 filaments. This fibre material has been cut into short fibre portions each having a length between 25 and 50 mm. The reinforcing mass is pre pared by blowing a stream of gaseous medium in which the fibres have been suspended into the aqueous mixture of Portland cement and sand thereby to provide a slurry of the fibres in the aqueous mixture. That slurry is applied to the precoat layers previously applied to the undulated surface of the mould portions. As shown in Figure 4, the two mould halves are then joined, the halves being brought together at an acute angle therebetween. The air present between the halves is pressed out by applying a light pressure to the upper portion of the mould. As a result of the pressing operation, the layers of each of the halves are combined with each other thereby to form the desired tile 6. The mould is then opened and the tile 6 is taken out therefrom with the thermoplastic undulated sheets in contact with the tile, to prevent water in the tile from being evaporated. The tiles are then stacked and left for about 24 hours.During that period, the initial curing of the Portland cement serving as a binder for the sand particles in the concrete takes place so that a tile consisting of fibre reinforced concrete is formed. After the curing has taken place, the thermoplastic sheets 3 can be easily removed from the two big surfaces of the tile 6 preferably by a suction device. The sheets can be used for the manufacture of new tiles. Figure 5 illustrates the removal of the sheets. The tiles can then be re-stacked and stored in a humid place for further curing for another three weeks or so (vide Figure 6). The edges of each tile can be trimmed and the corners cut off. The tiles can then be sprayed with a water-based acrylic paint unless colour pigment or granules are already present in the tile.

Alternatively, it is also possible to proceed in such a manner that the two layers, that is, the precoat layer and the main layer, are applied to previously shaped sheets of thermoplastic material without the latter being supported by the respective mould half. The sheets with applied layers are then joined and placed into the mould.

The mould halves are thus used only for the pressing operation thereby to yield the final dimension accuracy. This modified method presupposes that the thickness and rigidity of the undulated sheets of thermoplastic material are sufficient to prevent flattening of the sheets upon spraying the layers thereon. Instead of sheets of thermoplastic material it is possible to use any other shapeable sheet material, such as sheet steel.

It is possible by means of this method to produce a product of, inter alia, precise thickness, good surface finish, a high degree of homogenity and of high density in a sequence of application, pressing, curing and releasing steps.

As before mentioned, to prevent pockets of air or air-pores forming at the interface or contact surface between the applied quantities of material in the two mould halves, when the mould halves are pressed together, the mould halves, prior to and subsequent to the beginning of this pressing operation, are moved towards each other at an acute angle therebetween such as to bring the layers progressively into contact with one another. In this way it is possible to avoid, to a large extent air being enclosed within the material and the formation of pores in the pressed and cured product.

In accordance with a further embodiment of the invention, at least one of the mould halves is bendable and is curved, for example to parabolic shape, prior to moving the two mould halves together. Subsequent to beginning the pressing operation, the mould halves are gradually levelled out and are optionally completely levelled out upon completion of the pressing operation. When a mould is formable, bendable and bent in this manner, a high degree of precision must be expected of the press-plate urged by the press apparatus against the curved mould. The press-plate functions, together with the bendable mould, as the mould itself.During the pressing operation, one of the mould halves, both of which lie substantially horizontally on a supporting surface subsequent to the spraying operation, can be turned through 1800 by means of a gripping device or the like, and moved against the other mould half so that the quantities of sprayed material contained in said mould halves contact each other in a fully overlapping condition. It is assumed here, of course, that the applied material is of high viscosity and that adhesion between the surface of the turned mould half and the applied material is good, so that the contours of the material of the turned mould halves are not deformed or the material drops or falls from the moulding surface of the mould halves.

If the contours are likely to be deformed or the material is not likely to adhere satisfactorily to the moulding surfaces, each of the two mould halves is turned through only 90" by means of two gripping devices and moved to their rest position against each other with binding material applied by spraying between the mould halves.

A short time after fully completing the pressing operation, the package comprising the two mould halves and the pressed material can be freed from the pressing apparatus and turned to a horizontal position during the setting period.

It has been found particularly convenient to apply several layers of different binding or curable material mixtures onto each of the two mould halves and to press the laminated material composition between the mould halves in a single step. In this way it is possible to obtain relatively complicated laminated products which are well integrated and svmmetrical and which possess good structural properties.

Additional non-sprayable material, such as liquid adhesive, plastic binding compositions and rigid, optionally porous, structural plates can be placed between the layers applied by spraying prior to commencing the pressing operation or in conjunction with the commencement of said pressing operation.

The layered material compositions may be varied in many ways. Firstly, for example, there may be sprayed a thin layer containing an agent which affords the layer suitable release properties with respect to the mould but which preferably lacks a particulate additive. A setting or curable material, such as a binding cement composition or gypsum composition or a curable plastics product, preferably having a reinforcing additive, such as short glass fibres when the material is a cement mixture, is then sprayed in a thicker layer. This can optionally be repeated with the application of two or more similar sprayable and curable material mixtures.

Those layers located adjacent the surfaces of the mould but not constituting an outermost surface layer should be strongly reinforced. The large structural stresses namely occur close to the surface of a building element. For reasons of economy, fibres may be omitted from the thickness forming and/or acoustic and/or thermally insulating intermediate layers, or the amount of fibres incorporated within said layers may be far less than the amount of fibres in the layers adjacent the mould surfaces.

When an additional, non-sprayable material, such as a porous structural plate and plastics composition, is applied between the layers applied by spraying, the material itself will normally serve as a satisfactory binding system for the additional material, since, prior to the pressing operation, the materials applied by spraying are still wet and have not set or cured; furthermore the contact between the additional material and the applied materials is particularly good as a result of the pressure exerted thereupon during the pressing operation. In the case of certain combination of materials, it may be convenient to use a particular adhesive, which is also the case when no additional, non-sprayable material is used.

The adhesive may be poured between or sprayed against the applied layers of material on the surface of the mould halves prior to the pressing operation.

The method can also be used advantageously for producing structural plates having composite curvature by means of moulds exhibiting surfaces of multiple curvature, particularly when the plates must be manufactured with precise thicknesses and good surface finish. By way of example, a detailed description will be made below of the manner in which a cement roofing tile, of the so-called overtile type reinforced with glass fibres can be produced. Such a tile should not only have a good surface finish on both sides thereof, but the curvature of the tile and its thickness must lie within precise limits.

A first mould half manufactured from sheet steel and having a thickness of 1.5 mm and a second mould half manufactured from vacuum-shaped synthetic resin material and having a thickness of approximately 1 mm are placed on a conveyor belt passing beneath a series of spraying devices at a speed of approximately 0.1 m/sec.; each of said moulds having a moulding curvature corresponding to the desired curvature of the upper and lower surfaces of the roofing tiles. A thin layer of a substance effective to retard the binding of a cement mixture is sprayed onto both moulds.

A binding cement mixture containing glass fibres is sprayed onto the mould halves to a thickness of approximately 2.0 mm, by means of a spray nozzle which reverses perpendicular to the conveying belt at a speed of approximately 1 m/sec. The spraying pattern is of a pronounced elliptic configuration and have the same direction as the conveyor belt, so as to maintain minimum wastage at the mould edges extending parallel to the belt.Every point on the mould surfaces is covered by the spraying pattern approximately six times and the required thickness of the layer is ensured by controlling the amount of material sprayed per unit of time A cement mixture containing a considerably smaller quantity of glass fibres than the first mentioned cement mixture is sprayed to a thickness of approximately 1.5 mm on the first layer on the two mould halves, by means of a spraying unit arranged downstream of the first mentioned spray.

Subsequent to completing the spraying operation, the moulds on the conveyor belt enters a station provided with mechanical means which, by means of gripping devices, lift the mould halves 90" towards each other and press the mould halves together with the layers applied by spraying therebetween, until the distance between said mould halves is equal to the desired thickness of the roofing tile or approximately 7.0 mm.

The gripping device holding the second mould half, i.e. the support surface made of vacuum-shaped plastics material, is arranged to move said mould half towards the sheet-steel support surface or mould halves at a small angle between the two moulding surfaces of said mould halves, thereby to prevent the formation of air pockets and pores in the roofing tile. When the under edges of the mould halves con tact each other and the pressing operation commences, a thin, relatively highly viscous cement adhesive is poured in small quantities between the layers applied by spraying until the layers contact each other.

Fhe final pressing position is maintained for approximately five seconds, whereafter tile pressure is removed and the two mould halves with the pressed, laminate material composition is lifted in the form of a packet and placed in a horizontal position on other packets obtained in the same manner.

Subsequent to a setting and curing time of approximately 24 hours, the roofing tile is removed from the two mould halves. The thin layer of retarding agent between the two mould surfaces and the outer surfaces of the cement product facilitates parting of the cement product from the mould halves and therewith guarantees that the good surface finish is not impaired when separating said product from said mould halves.

A statistical survey of the thicknesses of twenty (20) corrugated cement roofing tiles reinforced with glass fibres and produced in the aforedescribed manner showed an average tile thickness of 7.0 + 0.5 mm and an average variation within each individual tile of 0.11 mm. A series of roofing tiles manufactured by spraying in a conventional manner gave an average tile thickness of 7.2 + 0.80 mm and an average maximum variation within each individual tile of 1.2 mm.

The flexural strength of sample rods sawn from roofing tiles produced as described with reference to the drawings was found to be greater than that of sample rods taken from tiles produced in a conventional manner: 32.1 t 1.0 MPa and 26.7 t 2.2 MPa respectively.

The finish on the upper and lower surfaces of the tiles manufactured by applying said settable material and pressing as hereinbefore described was superior to the finish of the surfaces of tiles manufactured in accordance with conventional methods but not pressed.

The tiles manufactured as described have also a better aesthetic appearance than tiles obtained in a conventional manner besides having a high resistance to frost and affording, as a result of the good finish on both the upper and lower surfaces of the tile, a pood seal in the overlapping zones of the tiles when laid on the roof.

WHAT WE CLAIM IS: - 1. A method of moulding an object from a setting material, such as to provide said object with two mutually opposing sides of a given configuration, said method comprising spraying a layer of said setting material onto a first support surface having the desired configuration of one of said sides, spraying a further layer of said setting material onto a second support surface having the desired configuration of the other of said sides, and while the setting material on the first and second support surfaces is still shapeable moving the charged first support surface towards the charged second support surface to form a mould such that the distance between said surfaces equals the desired thickness of the object, said surfaces being brought towards each other at an acute angle therebetween, so that the layers of setting material are pressed into the desired configurations progressively from one edge of each layer to the opposite edge thereof; applying a pressure to said mould to form the desired object, and removing the shaped object from said mould.

2. A method according to Claim 1, wherein a second setting material is applied to the first setting material on each respective support surface; wherein optionally a third setting material is applied to the second material on a respective support surface, prior to carrying out the pressing operation.

3. A method according to Claim 1 or Claim 2, wherein a material different to said setting material is applied between the layers on the first and second support surfaces prior to beginning the pressing operation or at the beginning of said pressing operation.

4. A method according to Claim 3, wherein the additional material is a liquid adhesive, a plastic binder, or a rigid structural plate.

5. A method according to Claim 3, wherein the additional material forms a light, porous core in the pressed and cured product.

6. A method according to any one of Claims 1 - 5, wherein the setting material applied to the support surfaces is reinforced, for example with glass fibre.

7. A method according to any one of Claims 1 - 6, wherein subsequent to charging the settable material to the support surfaces, said surfaces are moved from a horizontal position to a vertical position and pressed towards each other in said position, whereafter the support surfaces with the pressed material thereon are optionally returned to a horizontal position during the setting and curing period.

8. A method according to any one of Claims 1 - 6, wherein at least one of the support surfaces is bendable and is curved to, for example, a parabolic shape prior to moving the support surfaces together, said curved support surfaces being gradually flattened out in the pressing operation.

9. A method according to any one of Claims 1 - 8, wherein one or both support surfaces exhibits an undulating moulding

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

Claims (15)

**WARNING** start of CLMS field may overlap end of DESC **. tact each other and the pressing operation commences, a thin, relatively highly viscous cement adhesive is poured in small quantities between the layers applied by spraying until the layers contact each other. Fhe final pressing position is maintained for approximately five seconds, whereafter tile pressure is removed and the two mould halves with the pressed, laminate material composition is lifted in the form of a packet and placed in a horizontal position on other packets obtained in the same manner. Subsequent to a setting and curing time of approximately 24 hours, the roofing tile is removed from the two mould halves. The thin layer of retarding agent between the two mould surfaces and the outer surfaces of the cement product facilitates parting of the cement product from the mould halves and therewith guarantees that the good surface finish is not impaired when separating said product from said mould halves. A statistical survey of the thicknesses of twenty (20) corrugated cement roofing tiles reinforced with glass fibres and produced in the aforedescribed manner showed an average tile thickness of 7.0 + 0.5 mm and an average variation within each individual tile of 0.11 mm. A series of roofing tiles manufactured by spraying in a conventional manner gave an average tile thickness of 7.2 + 0.80 mm and an average maximum variation within each individual tile of 1.2 mm. The flexural strength of sample rods sawn from roofing tiles produced as described with reference to the drawings was found to be greater than that of sample rods taken from tiles produced in a conventional manner: 32.1 t 1.0 MPa and 26.7 t 2.2 MPa respectively. The finish on the upper and lower surfaces of the tiles manufactured by applying said settable material and pressing as hereinbefore described was superior to the finish of the surfaces of tiles manufactured in accordance with conventional methods but not pressed. The tiles manufactured as described have also a better aesthetic appearance than tiles obtained in a conventional manner besides having a high resistance to frost and affording, as a result of the good finish on both the upper and lower surfaces of the tile, a pood seal in the overlapping zones of the tiles when laid on the roof. WHAT WE CLAIM IS: -

1. A method of moulding an object from a setting material, such as to provide said object with two mutually opposing sides of a given configuration, said method comprising spraying a layer of said setting material onto a first support surface having the desired configuration of one of said sides, spraying a further layer of said setting material onto a second support surface having the desired configuration of the other of said sides, and while the setting material on the first and second support surfaces is still shapeable moving the charged first support surface towards the charged second support surface to form a mould such that the distance between said surfaces equals the desired thickness of the object, said surfaces being brought towards each other at an acute angle therebetween, so that the layers of setting material are pressed into the desired configurations progressively from one edge of each layer to the opposite edge thereof; applying a pressure to said mould to form the desired object, and removing the shaped object from said mould.

2. A method according to Claim 1, wherein a second setting material is applied to the first setting material on each respective support surface; wherein optionally a third setting material is applied to the second material on a respective support surface, prior to carrying out the pressing operation.

3. A method according to Claim 1 or Claim 2, wherein a material different to said setting material is applied between the layers on the first and second support surfaces prior to beginning the pressing operation or at the beginning of said pressing operation.

4. A method according to Claim 3, wherein the additional material is a liquid adhesive, a plastic binder, or a rigid structural plate.

5. A method according to Claim 3, wherein the additional material forms a light, porous core in the pressed and cured product.

6. A method according to any one of Claims 1 - 5, wherein the setting material applied to the support surfaces is reinforced, for example with glass fibre.

7. A method according to any one of Claims 1 - 6, wherein subsequent to charging the settable material to the support surfaces, said surfaces are moved from a horizontal position to a vertical position and pressed towards each other in said position, whereafter the support surfaces with the pressed material thereon are optionally returned to a horizontal position during the setting and curing period.

8. A method according to any one of Claims 1 - 6, wherein at least one of the support surfaces is bendable and is curved to, for example, a parabolic shape prior to moving the support surfaces together, said curved support surfaces being gradually flattened out in the pressing operation.

9. A method according to any one of Claims 1 - 8, wherein one or both support surfaces exhibits an undulating moulding

surface, both before and after the pressing operation.

10. A method according to any one of Claims 1 to 7, wherein each of said support surfaces comprises a rigid mould half.

11. A method according to any one of Claims 1 to 9, wherein each of said support surfaces comprises a sheet of flexible material, such as a sheet of shapeable thermoplastics material or sheet steel.

12. A method according to claim 11, wherein said support surfaces are placed into a respective mould half prior to said pressing operation.

13. A method substantially as hereinbefore described with reference to, and as illustrated in, the drawings forming part of this Specification.

14. An object manufactured in accordance with the method of any one of the preceding claims.

15. An object according to claim 14 wherein said object is a tile.