A known method which constitutes the prior art closest to the invention is described and illustrated in U.S. Letters Patent No. 4,092,393.

In an embodiment of this known method, a pack of flat slabs of marble or other ornamental stone is formed. The consolidated block obtained therefrom is subjected to multiple cutting perpendicular to the planes of the slabs to produce composite slabs having geometrical patterns determined by the contrast between the dif¬ ferent types of starting slabs.

The object of the present invention is to apply the principles of this known method to the production of composite panels of many different kinds starting from ready-cut slabs of different stone materials, sheets of reinforcing materials, etc.

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According to the invention, this object is achieved by a method wherein the pack is formed by positioning successive layers constituted by ornamental slabs of stone or equivalent material alternating with supple¬ mentary layers constituted by slabs or sheets in succession on a support base, the container is formed around the pack carried by the support so that a peripheral space is left in the container at least around the edges of the layers of the pack, the fluid binder is introduced into the container so that the binder completely fills the peripheral space and, after setting, constitutes a hermetic covering over the faces of the block corresponding to the edges of the layers, and the final multiple cutting of the block is carried out along the intermediate planes of some layers in order to produce the panels.

The method according to the invention is suitable for the formation of panels including any type of stone but particularly granite slabs.

Document WO 89/11958, which was published after the priority date of the present application, describes and illustrates a method in which reinforced panels are produced by the cutting or sawing of a block of construction material such as stone. It is difficult to produce panels incorporating granite slabs bythis method.

In the method of Document WO 89/11958, ^■ one starts with a block which is subjected to multiple cutting. The size and shape of the block must be compatible with the dimensions of a form. In the case of marble, the block can easily be squared off if it does not have this size or shape. With granite, however, this is not possible at a reasonable cost. The squaring of granite

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blocks is an unusual operation in normal practice. The granite block is usually sawn without being squared so that slabs of very varied dimensions are obtained.

The method of the invention enables the pack to be formed with the use of slabs of substantially the same size, after this size has been selected from the various sizes available.

A method for the production of composite panels each including a layer of stone and a reinforcing layer which in turn is composite is known from European Patent Application No. 252,434.

In order to make these panels, composite elements are formed, each including two opposite outer layers of stone and/or interposed reinforcing layers. These elements are combined in a pack with the interposition of spacers and the spaces between the elements are at least partly filled with a filler material. The pack thus produced is clamped in a press and sawn along the median planes of the stone slabs.

Amongst other things, this known method has the disad¬ vantage that it does not allow the best use to be made of the space occupied by the pack, given the presence of the spaces containing the filler material which is to be discarded. Moreover, it does not permit the improvement of the stone by in-depth impregnation.

Further characteristics and advantages of the invention will be understood better from a reading of the de¬ tailed description which follows with reference to the appended drawings, provided purely by way of non-limiting example, in which:

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Figure 1 is a perspective view of a support structure during preparation for the formation of a pack of slabs or layers, according to a first embodiment.

Figures 2 and 3 respectively are a plan view and a side view of the same structure during the formation of a pack of layers,

Figure 4 is a side view corresponding to Figure 3 but showing another embodiment of the structure,

Figure 5 is a detailed perspective view showing a system for detecting the positions of the slabs during the formation of the pack in order to position the cutting planes correctly,

Figure 6 is a schematic representation of the posi¬ tioning procedure achieved with the aid of the system of Figure 5,

Figure 7 is a perspective view showing the various elements of a container during its formation around the pack of layers,

Figure 8 is a plan view of the container formed around the block, and of the block itself, from above.

Figure 9 is a longitudinal section taken on the line IX-IX of Figure 8,

Figure 10 is a section corresponding to Figure 9 of the consolidated block alone, and

Figure 11 is a partial section taken transverse the slabs of the block, showing some of the various kinds

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of composite panels which can be obtained by the method according to the invention.

With reference to Figures 1 to 3, a strong metal support structure is generally indicated 10. The structure 10 includes a base wall 12 and a side wall 14 fixed firmly together and arranged at right angles.

In order to form a pack of layers or slabs, as will be described further below, the two walls 12 and 14 are preferably inclined at a certain angle alpha of a few degrees, for example, with the use of hydraulic jacks 16.

The base wall 12 has a flat load-bearing surface 18. The side wall 14 also has a flat surface 20 at the side of the surface 18.

In preparation for the formation of a pack of layers on the support structure 10, the load-bearing surface 18 is preferably covered with a flooring 22 of reject slabs of marble or other stone, for the purpose which will be explained below.

Spacer elements 24, preferably in the form of strips of wood or other material, are positioned in a staggered arrangement on the flooring 22, for the purpose which will be explained below.

Further spacer elements in the form of strips 26 are formed on or applied to the surface 20 of the side wall 14, again for a purpose which will be explained below.

Once the operations described above have been carried out, a pack P of layers of slabs L is built up,

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starting from the side wall 14 with the first slab L resting against the spacer strips 26. The formation of a tight pack is facilitated and maintained by the downward inclination of the load-bearing surface 18 towards the side wall 14 and by the outward inclination of the surface 20 of the latter.

A support structure such as that indicated 10 is preferably of such a size that it can hold slabs of the longest length available commercially. For example, it may be arranged to hold slabs 3.50 m long by 1.55 m wide.

If the pack P is composed of shorter slabs, it is envisaged that a box-shaped filler element 28 will be used to fill up the space not occupied by the pack P in the container, as will be mentioned further below. The support structure 10 may be provided with an assortment of boxes 28 of different dimensions for use in depend¬ ence on the lengths of the slabs.

Figure 4 shows the same support structure 10 tilted through 90° with respect to Figure 3, its parts being indicated by the same reference numerals as in the preceding drawings.

In the embodiment of Figure 4, the pack is formed by laying successive layers or slabs L flat on top of one another, starting from the base wall 14 or rather from its spacer elements 26.

To advantage, the layers, or at least the heavier slabs L, are positioned by apparatus 30 with suction cups 32.

In the embodiment of Figure 4, the two walls 12 and 14

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are preferably also inclined so as to ensure that the successive slabs L abut the spacer strips 24 of the side wall 12 which are applied in turn to a covering of tiles or slabs 22.

After the pack P has been formed, the structure 10 of

Figure 4 is tilted to the position of Figure 3 for the pouring of the binder which will be mentioned further b low.

With reference again to the embodiment of Figures 1 to 3, during the formation of the pack P, reinforcing ties, indicated 34 in Figures 7 and 8, are preferably glued to its upper face at intervals. These ties may simply consist of reject slabs of marble or other material glued to the slabs during the formation of the pack. Alternatively, the ties could consist of U-shaped metal brackets arranged astride two or more consecutive stone slabs.

A convenient system for the correct positioning of the slabs of the pack will now be described with reference to Figures 5 and 6.

Figures 1 and 2 show schematically two devices, indi¬ cated 36, which are fi.ed along the two opposite ends of the lower wall 12 during the formation of the pack P.

Each device 36 comprises an elongate frame 38 which carries a guide rod 40 and a threaded rod 42 parallel to the former. The device 38 is arranged such that the two rods 40 and 42 extend parallel to the direction in which the pack P of slabs L is built up.

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The device 38 also includes a strip 44 which is paral¬ lel to the rods and acts as a fixed scale. The gradua¬ tions of the scale are constituted by holes 46 formed in the strip 44. The spacing of the graduations or holes 46 will be mentioned further below.

A carriage 48 is slidable on the two rods 40 and 42 and has a female thread (not shown) which is engaged on the threaded rod 42. The rotation of a wheel 49 causes the carriage 48 to slide along the guides constituted by the rods 40 and 42.

The carriage 48 carries a laser gun 50 which projects a laser beam so as to form a line of light 52 substan¬ tially parallel to the corresponding edges of the slabs L.

By way of example, a peg 53 is mounted on the carriage 48 for snap-engagement in successive holes 46.

With reference to Figure 6, the holes 46 are arranged at the cutting pitch PT of a multiple cutting frame whose cutting members {blades, diamond wires, or the like) are indicated BL. The spaces PT between one blade and another may differ and are arranged according to the cuts to be made in the block which is produced from the pack of layers P and which will be mentioned further below.

The cutting planes which must correspond precisely to the positions of the blades BL during the final multi¬ ple cutting are indicated CP in Figure 6. These cutting planes CP will be in slabs LS which form parts of the pack and between which are interposed one or more intermediate layers IL having reinforcing or other

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functions in the composite panels to be produced.

It is assumed that the formation of the pack has reached the stage of the positioning of a slab LS, in which a cut is envisaged along a median cutting plane CP, . The slab LS, may be of stone or another material, for example asbestos cement, as will be seen below.

When the operator has positioned the slab LS, (Figures 5 and 6), he moves the carriage 48 with the aid of the wheel 49 so that the peg 53 is engaged in the hole 46 which corresponds to that slab. The gun 50 thus projects a line of light 52 onto the slab LS.. If the line of light 52 is offset from the envisaged cutting plane CP, , for example, by an error of a magnitude -Λ as shown in Figure 6, the operator takes account of this difference in the positioning of a subsequent slab LS _? to be cut along a cutting plane CP _? . It should be noted that the positioning errors /\ from one slab to the next are generally negligi¬ ble (of the order of 1 mm) in comparison with the overall thickness of a slab such as LS, (of the order of 4-5 cm) so that one cutting error in either direc¬ tion from the envisaged cutting plane CP, is of little importance.

The operator must bear in mind that the error LA - has to be compensated for in the next slab LS ₂ to be cut. In order to compensate for the error, the operator selects, from an available stock, one or more interme¬ diate layers IL or shim sheets provided for in the composition of the pack and having a thickness such as to compensate, in the next intermediate cutting plane CP _? , for the error found in the preceding cutting plane CP, . The shim sheets or layers selected may be intended

to form part of a corresponding final composite panel or, as will be seen, may be expendable separating layers.

The use of a line of laser light 52 serves not only to check whether or not a cutting plane such as CP, corresponds to the envisaged cutting position but also to check that a slab such as LS, is parallel to the previously positioned layers of the pack and to make it parallel if necessary. This may be done at the two ends of the slabs, preferably with the use of two detection devices, as indicated 36 again in Figures 1 and 2.

The devices 36 are removed before the formation of a casting container which will now be described.

With reference to Figures 7 to 9, the structure 10 is used as part of a container for the casting of a fluid binder, as will be described below.

The container, generally indicated C, is generally in the shape of a box which is open at the top. Its base wall and one of its side walls are constituted by the base wall 12 and the side wall 14 of the structure 10, respectively. The other walls of the container consist of two end walls 54 and a second side wall 56. These three walls 54 and 56 are bolted to the edges of the walls 12 and 14 and to each other or are connected by some other rigid clamping system (not shown) with the interposition of sealing strips (not shown). Prefera¬ bly, the side wall 56 also includes strips or other spacer elements 58 (Figure 8) similar to the strips 26.

The filler element 28, if used, is left in the con¬ tainer or box C beside one end wall 54 to prevent the

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undesirable filling of that space by the binding material .

As can be seen in Figures 7 to 9, a peripheral space remains between the pack P and all the walls of the container 50. In particular, there is a region 60 of the peripheral space between the flooring 24 and the lower face of the pack P and there are lateral regions 62 of the space between the pack and the side walls 14 and 56. There are also regions 64 and 66 of the space between the filler element 28 and the respective end wall 54. These regions 64 and 66 of the peripheral space are formed simply by the careful and correct centring of successive slabs of the pack P.

The box C and the pack P contained therein are sub¬ jected to an impregnation operation according to the teaching of U.S. Patent Specification

No. 4,013,809, to which reference should be made.

In particular, the unit constituted by the container and the pack is first of all subjected to a step of drying and preheating in order to remove any water impregnating the material of the pack P.

Preferably, however, the drying and preheating step is carried out on the stone slabs before the pack P is formed.

In this case, it may be necessary to heat the pack P if the impregnation, to which further reference will be made below, is carried out several hours after the formation of the pack, for example, on the following day.

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The impregnation is carried out in an autoclave ac¬ cording to the teaching of U.S. Patent Specifications Nos. 4,013,809 and 4,092,393, to which reference should be made for all the details.

For simplicity, the term "resin" will be used in the following description to indicate any suitable, setta- ble fluid product. Two-part, so-called thermosetting synthetic resins (epoxy, polyester and other resins) are preferred, however.

In any case, it is envisaged that the impregnating resin will have the characteristic of setting within a longer or shorter time period by internal chemical transformation which, upon completion, causes it:

- to adhere strongly to all the walls of the space occupied except for the not-stick layers which will be mentioned.

to acquire a mechanical strength substantially comparable to that of the stone or other material with which it is in contact.

According to a preferred embodiment, the impregnating resin is introduced into the box C, as in U.S. Patent Specification No. 4,092,393 by pouring from above through a suitable distribution system, under a high vacuum. With this method, the layers of the pack P are dried further still and the liquid resin is degassed at the moment of introduction.

During the pouring, the resin spreads into all the gaps between the individual slabs L of the pack, descends in the peripheral space through its side regions 62, 64,

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66 and, after it has spread into the lower space 60 along the labyrinthine path defined by the strips 24, rises into the gaps between the slabs L to impregnate them completely.

The introduction of the impregnating liquid is stopped when the pack P is submerged under a head of several centimeters of liquid, as shown at 70 in Figure 9.

According to a variant, the same container in which the pack P is situated may be closed hermetically by means of a lid (not shown) so as to act as an autoclave.

If the stone is so compact as not to necessitate the penetration of the resin into small spaces in the heart of the material (deep penetration) and if the other sheets or slabs provided, as mentioned further below, are of a type and shape such as to enable the whole surface to be wetted well at the stage of introduction of the resin filler, the actual impregnation of the materials may not be necessary.

In most cases, however, these conditions do not occur since stone inevitably has some defects, spaces, etc., so that actual impregnation is necessary. This impregnation is achieved, according to the teaching of U.S. Patent Specification No. 4,013,809, by the appli¬ cation in the autoclave (and/or in the hermetic con¬ tainer) of an overpressure which acts on the liquid resin before it sets and forces it to occupy all the cavities (spaces, cracks and other defects) in the stone and possibly in the other layers.

As described in U.S. Patent Specification No. 4,013,809, the overpressure may consist simply of the

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return of the interior of the autoclave or container to atmospheric pressure, resulting in a differential pressure on the free surface of the resin.

Once the resin or other binder has set, a composite block 72, as shown in Figure 10, is obtained, in which all the gaps between the layers and all the spaces or cavities in the individual layers have been filled with resin. Moreover, the block 72 is completely encapsu¬ lated in a layer 74 of set resin or other binder which seals its interior. The various layers within the block 72 are thus kept firmly stuck together, not only by the resin which binds them but also by the atmospheric pressure around the envelope 74. This is particularly useful, above all, when there are non-stick layers in the block 72, as will be seen below.

The advantages of the flooring 22 shown in Figure 1 will now be explained with reference to Figure 10. This flooring remains bound to the lower face of the block 72, which will be cut last during the multiple cutting process, by the resin or other binder.

Particularly in the case of granite, the cutting is carried out by means of blades which wear out quickly. The blades wear more at their centres than their ends, so that they assume an arcuate shape, as shown at 76 in Figure 10. It is thus desirable that, when a blade reaches a condition such as that indicated 76a in Figure 10 towards the end of the cut, its ends still find a material similar to that of the block to cut or saw below the block 72. The flooring 22 in fact con¬ stitutes this material and is sawn partially at the ends whilst the centres of the blades complete the cutting or sawing of the centre of the block 72.

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The flooring 22 incorporated in the block 72 also constitutes a base for the block and protects its lower face during handling.

Some of the various possible compositions of the pack P and the panels which can be produced therefrom will now be described with reference to Figure 11.

In Figure 11, the envelope or capsule of resin or other binder is again indicated 74. The cutting planes are again indicated CP. The slabs to be cut along the planes CP are indicated by the reference letters LS followed by suffix letters.

The panels to be produced by the cutting along the planes CP are indicated by the letters PN followed by suffix numerals.

Reinforcing layers of various kinds are indicated RL.

Certain reinforcing layers, which will be mentioned further, are indicated RG. Separating layers are indicated SL.

The separating layers SL may consist of thin, rigid or flexible sheets of a material, such as a sheet of polyethylene, having the property that it does not stick to the resin or other binder. Alternatively, the separating layers SL may be actual layers of a non-stick material, such as silicone oil, spread on the mating faces of the two adjacent slabs or sheets. The separating layers SL may also be disposed, for example glued, on one or other of the faces of the adjacent layer.

The reinforcing layers RL may be constituted by sheets

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or slabs of a solid material which is intended to remain joined to a layer of ornamental material, such as LS, in a final composite panel, such as those indicated PN. For example, a reinforcing layer may be constituted by a fibrous material, such as glass fibre, by a piece of sheet metal, perhaps perforated, or by a mesh of metal or other material. Other materials for the reinforcing layers may be fabrics or mats of glass fibres or the like, or laminated plastics sheets. The use of asbestos cement for the reinforcing layers is also envisaged. In this case, the slabs such as LS may be of asbestos cement and may be intended to be cut along the planes CP.

In one particular case, a reinforcing layer may be constituted by a sheet of glass RG.

Preferably, as shown in Figure 11, the layers, such as RL and SL, which are not intended to be cut are of such a size that their edges are recessed from the upper face of the block B. Gaps are thus formed between the tops of the slabs LS which are intended to be cut and are filled by bridges 78 of set binder. This measure is particularly useful when the slabs LS to be cut are of granite. In this case, the cutting is carried out from the upper face of the block B with the aid of abrasive metallic grit. Without the bridges 78, the grit, which covers the whole upper face of the block, would erode the top edges of the layers such as RL and SL with a disastrous "breaking of the vacuum" which keeps the separating layers SL and the adjacent layers together during the cutting along the planes CP.

Separation is carried out, however, in order to obtain the individual panels PN after the cutting or sawing of

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the block B along the planes CP and after the removal of the en ^* iope of binding material 74.

Still with reference to Figure 11, two panels such as

PN.. and PN ₂ , produced by cutting through the middle of the slab LS and separating the rest of the block B by virtue of the non-stick layer SL, may each include a layer of stone and one or more reinforcing layers RL of one or more of the aforesaid materials. Panels such as PN- and PN. , produced by separation in the same way, may include a different stone.

Two panels such as PN ₅ and PN, may each include a layer of marble produced by cutting through the middle of the slab LSc the visible surface of which is covered by a respective transparent layer of glass RG. Sheets of this type were previously produced by a fairly complex method described and illustrated in U.S. Patent Speci¬ fication No. 4,460,850. According to this method, a transparent sheet of glass was fixed to a stone slab by means of a sheet of polyvinyl butyral.

A panel PN ₇ may include a pair of slabs LS, and LS of stone, or a slab of stone and one of asbestos cement, joined together permanently with the interposition of one or more reinforcing layers RL of one or more of the types mentioned above. Reference should be made to U.S. Application SN 458,693 for other possible compositions of the composite panels.

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