METHOD FOR CONSOLIDATING NATURAL STONE BLOCKS FOR SUBSEQUENT SAWING Technical field

The present invention relates to a method for consolidating natural stone blocks, particularly marble and granite, for subsequent sawing. Background art

The cutting of natural stone blocks in order to obtain slabs of various thicknesses generally entails, during cutting, the breakage or at least fraying of the slabs. This has created the need to provide methods aimed at consolidating the blocks to be sawed, in order to avoid or at least reduce the waste of material caused by cutting.

Known methods currently in use for securing natural stone blocks before sawing them can be grouped substantially into three types: a) consolidation with mat and resin; b) consolidation with marble plates and mastic; c) consolidation with wood, resin and inert materials.

The first type, i.e., consolation with mat and resin, provides for the application of a bidirectional fiberglass mat on the faces of the block to be cut, which is subsequently impregnated with epoxy resin (500 g of resin are required for every 500 g of mat).

The second type, which provides for the consolation of the blocks with marble plates and mastic, is considered the most archaic method among known ones and consists in fixing pieces of waste marble slabs to the block to be cut, by using large amounts of polyester mastic. The lack of regularity of the profiles of the blocks to be cut and the fact that the marble slabs used originate from work waste constitute a complication in performing the described method.

The third type of consolidation is the one currently most widely used and consists in providing, by using mastics or putties, a frame made of wood or plywood around the block to be cut, so as to form a sort of containment

cage inside which resin and inert materials of various sizes are poured, obtaining, at the end of the process, an almost regular profile of the block.

These known types of method are not free from drawbacks, which may be described as follows in relation to the type of application. Consolidation with a mat and resin requires rather long execution times, which can be estimated on the whole as being on the order of approximately two days for each block to be treated, due partly to the reaction times of the epoxy resin; however, these times can undergo variations if the operator makes mistakes in the dosage of the parts in order to make the mat adhere perfectly to the block.

Consolidation with marble plates and mastic also requires one or two days for its execution, in addition to the fact that, as mentioned earlier, the irregularity of the profiles of the blocks to be secured and the approximate and often uneven dimensions of the marble plates used make the application difficult and scarcely effective.

Finally, consolidation with wood or plywood, while being the substantially most efficient method among the ones described, also requires distinctly long times, on the order of four or five days per block, for its execution, and further entails substantial costs, due also to the use of material, such as wood or plywood, to manufacture the block containment cage, which necessarily has to be destroyed at the end of the process, thus preventing recovery of the used material.

Moreover, it is noted that these methods are performed generally in the open air and therefore long execution times entail the substantial risk that the outcome of the consolidation might be penalized for example in case of bad weather. Disclosure of the invention

The aim of the present invention is to provide a method for consolidating natural stone blocks for subsequent sawing which allows to reduce significantly the time required to secure the blocks before sawing

them, ensuring optimum effectiveness of the treatment.

Within this aim, an object of the invention is to provide a method which is easy to perform and safe in operation.

Another object of the invention is to provide a method which entails a modest use of auxiliary materials, consequently reducing the application costs.

Another object of the present invention is to allow easy and safe transport of the natural stone slabs obtained by sawing.

Another object of the invention is to provide a method which allows to reduce the waste material caused by its execution.

This aim and these and other objects, which will become better apparent hereinafter, are achieved by the present method for consolidating natural stone blocks to be subjected to subsequent sawing along at least one predefined cutting plane, characterized in that it comprises the step that consists in applying at least one layer of polymeric resin to at least one face of a block to be cut which is intersected by said cutting plane. Brief description of the drawings

Further characteristics and advantages of the present invention will become better apparent from the following detailed description of a preferred but not exclusive embodiment of a method for consolidating natural stone blocks for subsequent sawing, illustrated by way of non- limiting example in the accompanying drawings, wherein:

Figure 1 is a perspective view of the step of application of the layer of polymeric resin to the lateral faces of the natural stone block; Figure 2 is a top plan view of the natural stone block after the application of the polymeric resin;

Figure 3 is a perspective view of the step of distribution of polymeric resin on the upper face of the natural stone block;

Figure 4 is a sectional front elevation view of the natural stone block after the application of partial vacuum and the distribution of polymeric

resin on the upper face of the block;

Figure 5 is a sectional front elevation view of the natural stone block after the application of the partial vacuum and the distribution of pressurized polymeric resin on the upper face of the block; Figure 6 is a perspective view of the natural stone block and of the slabs obtained by sawing. Ways of carrying out the invention

According to a preferred embodiment, illustrated by way of non- limiting example in the figures, the reference numeral 1 generally designates a natural stone block, having a substantially parallelepipedal shape, which is to be sawed. In practice, the geometry of the block 1 can be rather irregular but substantially similar to a parallelepiped.

The method according to the invention provides for the application, preferably by spraying, for example through one or more nozzles 2, of at least one layer 3 of polymeric resin on one or more faces 11 of the block 1 which are intersected by predefined cutting planes 4, for example 4a and 4b, which are adapted to adhere to said faces for consolidation of the block 1.

Preferably, application of the layer 3 occurs continuously so as to define a uniform coating of the faces 11. As an alternative, application of the layer 3 may occur discontinuously, for example by forming a plurality of strips which are perpendicular to the cutting planes 4.

To ensure optimum effectiveness of the treatment, the layer 3 must be applied to all the faces 11 intersected by the cutting planes 4, so as to form a sort of frame of said block and of the slabs obtained from it by sawing. The layer 3 thus applied enters the cracks and fissures that may be present on the surfaces of application, thus also penetrating into the block 1 so as to optimize its consolidation.

The duration of the step of application of the layer 3 is a function of the thickness to be obtained, which varies depending on the characteristics of the material that constitutes the block 1, on the defects that are present on

the surfaces to be treated, and on the type of resin used. The layer 3 can be obtained in one or more passes.

The polymeric resin used is preferably of the thermosetting type, for example a compact or expanded polyurethane or epoxy resin. For compact polyurethane resins, the thickness of the layer 3 is comprised generally between 3 and 10 mm, whereas for expanded polyurethane resins it can vary between 15 and 30 mm.

Once application has ended, the resulting layer 3 begins to harden so that it sets on the faces 11 ; the duration of the hardening step is a function not only of the thickness of the resulting layer 3 but also of the type of resin used and of the environmental conditions.

The duration of the hardening step can vary from 1-2 minutes to 1-2 hours.

If one wishes to further increase the compaction of the block 1 , it is possible to apply a partial vacuum at at least one portion, not associated with the layer 3, of a first face 15 of said block which is preferably not intersected by the cutting plane 4, and distribute an amount of polymeric resin 6 at at least one region, not associated with the layer 3, of a second face 16, which also preferably is not affected by the cutting plane 4. Conveniently, at least one of the first and second faces 15 and 16, and preferably both, are substantially parallel to the cutting plane 4 and are mutually opposite.

The resin 6 is preferably of the epoxy type, but it may also be of the polyurethane type or of another type. In a particular embodiment of the method according to the invention, the first and second faces, respectively 15 and 16, are not associated with the layer 3 and the step for distributing the resin 6, performed by spraying for example with the aid of a nozzle 2 or by pouring, occurs in discrete quantities at the fissures which can be detected on the second face 16 so as to avoid waste, but it might also be distributed continuously so as to cover

the second face 16.

It should be noted that the impermeabilizing effect caused by the application of the layer 3 to the faces 11 allows to optimize the penetration of the resin 6 applied to the second face 16 within the block 1, since the faces 11 are isolated from the outside environment and therefore no dispersions occur.

The drawing action which affects the block 1, oriented in the direction 7 and caused by the partial vacuum applied at the first face 15, facilitates, by way of the porosity of the material, the penetration of the resin 6 within the block 1 and the filling of any fissures which might be present on the surface of application.

During this step, known as resin encapsulation, the block 1 preferably rests at the first face 15, so as to also use gravity, in addition to the drawing action described above, to facilitate the penetration of the resin 6. The amount of resin 6 to be distributed on the second face 16 varies substantially as a function of the defects of the block 1 which emerge at said face and are possibly connected to internal defects, and as a function of the characteristics of the material and of the type of resin used.

In a preferred embodiment, shown in Figure 5, the step of distributing an amount of resin 6 is performed under pressure, in order to improve its penetration into the block 1 and optimize its consumption.

In the embodiment shown in Figure 5, distribution of the resin 6 is performed by using at least one dispensing device 30, which is connected to a pump and is arranged at a first region of the second face 16 which is not associated with the layer 3 and is conveniently chosen depending on the concentration and extent of the fissures that are visible externally.

Advantageously, the dispensing device 30 comprises at least one branch 31 which is adapted to distribute an amount of resin also at a second region of the second face 16, which is also not associated with the layer 3, in order to reach simultaneously the most critical areas.

Application of a partial vacuum at the first face 15, conveniently performed simultaneously with the distribution of the resin 6, is performed by arranging at least one vacuum pump 32 at at least one portion of the first face 15 which is not associated with the layer 3. Advantageously, at least one of the first and second faces 15 and 16, preferably both, is associated with the layer 3 of resin. Conveniently, the layer 3 is applied to all the faces of the block 1 and in practice covers it.

More precisely, the application of the layer of resin 3 to the first and/or second faces 15 and 16 occurs respectively after the arrangement of the dispensing device 30 and/or of the vacuum pump 32.

Conveniently, the application of partial vacuum at the first face 15 and the distribution of resin 6 at the second face 16 are performed after the application of the layers 3.

In this manner, the block 1 does not have areas which can be accessed from the outside and the layers 3 deposited on all the faces of the block 1 have a containment effect which increases the effectiveness of the partial vacuum applied at the first face 15 and of the pressure with which the resin

6 is distributed at the second face 16, forming a sort of preferential channel for the flow of the resin within the block 1 which is adapted to enhance the penetration of the resin 6.

Finally, before proceeding with the sawing step, it is necessary to wait for the resin 6 to harden in order to achieve complete consolidation of the block 1.

In practice it has been found that the method according to the invention achieves the intended aim and objects, since it allows to perform consolidation of the block to be sawed by applying a layer of resin to the faces affected by the cutting action, reducing the time required for its execution and the use of auxiliary materials.

In particular, the execution times of the method according to the invention are on the order of magnitude of a few hours, increasing

productivity significantly with respect to known methods.

The reduction of the execution times and the simplification of the operations required are particularly appreciable if one considers that said procedures are usually performed in an open environment, sometimes directly in a quarry, and by personnel which is not particularly qualified.

The invention thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the appended claims.

All the details may further be replaced with other technically equivalent elements.

In practice, the materials used, as well as the contingent shapes and dimensions, may be any according to requirements without thereby abandoning the scope of the protection of the appended claims.

The disclosures in Italian Patent Application No. MO2006A000216, from which this application claims priority, are incorporated herein by reference.