METHOD FOR OBTAINING REINFORCED SLABS OF STONE MATERIALS AND SLABS OBTAINED BY SAID METHOD

Abstract: The present invention relates to a method for obtaining reinforced slabs of stone materials. The invention also relates to reinforced slabs of stone materials, in particular marble and similar stone. Said method comprises the step of applying at least one sheet (2) of carbon fibre to a face of a slab (1) of stone material.

Description: DESCRIPTION "METHOD FOR OBTAINING REINFORCED SLABS OF STONE MATERIALS AND SLABS OBTAINED BY SAID METHOD" The present invention relates to a method for obtaining reinforced slabs of stone materials. The invention also relates to reinforced slabs of stone materials, in particular marble and similar stone. The term "similar stone" is intended to mean stone which can be worked like marble, such as, for example, granite and semi-marble limestone. Marble and said similar stone exhibit characteristics of workability, stability, durability and colouring such as to render them particularly suitable for use in the building industry. Moreover, their susceptibility to acquiring good smoothing and polishing allows them to be used as outstanding decorative stone. Blocks of marble and of similar materials are commonly cut into slabs which are subjected successively to various treatments such as smoothing and polishing. Once treated, such slabs can be reduced to the desired dimensions and marketed. During the various changes which lead to the finished product, drawbacks may arise which are linked to the fragility of the cut slabs. This problem occurs especially when their thickness is somewhat reduced, thus being able to lead to breakages. Consequently, there is a strong need to provide slabs of marble or of similar materials having a certain robustness which will permit them to be handled without causing breakages, therefore favouring the practicability of their use and moreover allowing their easy industrial preparation. The problem underlying the present invention is therefore that of providing a method which makes it possible to obtain slabs of stone materials having a certain robustness and which have structural and functional characteristics such as to satisfy the aforesaid requirements and at the same time to avoid the drawbacks exhibited by the slabs of the prior art . Said problem is solved by a method as described in claim 1. A further subject of the present invention are slabs of stone materials strengthened as described in product claim 16. The method of the present invention provides for the application of at least one sheet of carbon fibre to a face of a slab of stone material . Preferably, said sheet of carbon fibre consists of a sheet of carbon fibre fabric. Further characteristics and advantages of the slabs of stone materials according to the present invention will become clear from the following description of one of their preferred exemplary embodiments, provided by way of non-limiting example, with reference to the appended drawings, in which: Figure 1 shows a perspective view of a slab of stone materials according to the invention; Figure 2 shows an exploded view of the slab of stone materials of Figure 1. The reference 1 indicates as a whole a slab of stone material to which a sheet 2 of carbon fibre is applied. Said sheet 2 of carbon fibre preferably consists of a sheet of carbon fibre fabric which is suitably cut so as to substantially cover a face of the slab 1. The carbon fibre fabric is more preferably that supplied by the company SIKA which is indicated by the name Sika rap 160 C. The particular function of the carbon fibre applied to a face of the slab of stone material is that of providing the slabs themselves with significant mechanical strength. This function becomes obvious above all when the carbon fibre is applied to thin slabs having a thickness of less than 1 cm. , preferably to slabs having a thickness of between 0.3 cm and 0.7 cm, more preferably to slabs having a thickness of about 0.5 cm. The advantage which is obtained, in fact, is that of being able to handle such a thin slab without risk of breakage . Consequently, it will therefore be possible to obtain more slabs from a single block of stone material, with a significant saving on the material used. Among the stone materials which may be used in the present invention, those of particular interest are the so-called marbles or limestones having a saccharoid or spar-like texture, semi-marble limestones, granites or other types of stone, but which are in any case capable of being smoothed and polished, suitable for being used in the building industry. The method for obtaining a slab of stone material according to the present invention comprises the steps of: a) applying a layer of resin to one of the two faces of said slab; b) applying at least one sheet 2 of carbon fibre to said layer of resin. Preferably, steps a) and b) are followed by step c) of applying a sufficient pressure to said sheet to incorporate said sheet in said resin. To obtain a greater strengthening effect, steps a), b) and optionally c) are carried out repeatedly on the same slab . The sheet of carbon fibre preferably may consist of a sheet of carbon fibre fabric. Said sheet may be that supplied by the company SIKA, under the name of Sikawrap 160 C. Said resin may in particular be an epoxy resin and, more particularly, may be the resin known as Sikadur-330 L VP supplied by the company SIKA. Step c) may be carried out preferably by means of rolling. To obtain improved incorporation of the layer in the resin, it is preferable to apply a second layer of resin after step b) or c) . The method further comprises a step d) of drying the resin. The drying of the resin may take place in air or preferably in an oven. The method described above may further comprise the following steps carried out upstream: a') cutting blocks of stone rock into groups of one or more slabs having a thickness of less than 1 cm spaced by a slab having a thickness of more than 1 cm; b ' ) applying a removable support to a face of each of said slabs having a thickness of less than 1 cm. Preferably, said cut slabs have a thickness of between 0.3 and 0.7 cm, more preferably of about 0.5 cm, and are spaced by a slab having a thickness of about 2.5 cm. The removable support may be a framework of any rigid material suitable to be used in an oven, and preferably may be a baking support . As may be noted, this method advantageously makes it possible to obtain particularly thin slabs which however are reinforced by means of the application of the sheet 2 of carbon fibre in a step immediately following the cutting step. In particular, the use of a slab of greater thickness spacing one or more thin slabs imparts sufficient robustness to the group of said slabs so that they can be handled for the application of a temporary support . Said temporary support allows normal moving operations, avoiding the risk of breakage of the slabs. It is obvious that said steps may be carried out rapidly with the final result of a slab which has the optimum properties of mechanical strength in spite of the reduced thickness dimensions. In the example which follows, a detailed description is given of an exemplary embodiment of the method for obtaining a reinforced slab of stone material according to the present invention, provided by way of non-limiting example . EXAMPLE A block of stone material is cut with frame saws so as to obtain groups of five slabs having a thickness of about 0.5 cm, spaced by a slab having a thickness of about 2.5 cm. The thickness of the cut slabs may vary by + 20% by reason of the limits of accuracy involved with saw frames. To the slabs of about 0.5 cm thickness there is then applied a baking support which has a metallic strengthening frame and an abutment shoulder so as to allow secure support and movement of the slabs. The baking support may be held firmly in contact with the slab by means of clamps spaced along the margin of the slab. The slabs clamped by the table are positioned horizontally on a plane so as to bear on the baking support and be ready for the application of the carbon fibre to the exposed face. The operations of moving of the slabs which follow cutting may be carried out by means of mechanized systems which comprise, for example, a cushion of air on which to support the cut slabs . A layer of Sikadur-330 L VP epoxy resin is spread with a roller or with a brush on the surface of the slabs. A sheet of SikaWrap 160 C carbon fibre fabric is then applied so as to protrude slightly from the edge of the slabs. The slabs are then rolled so as to obtain complete impregnation of the fabric in the layer of resin. The slabs are then placed in an air oven at a temperature of 40°C for 2 hours. Finally, once the slabs have emerged from the oven, the carbon fibre sheet protruding from their edge is trimmed off and the slabs are ready to be smoothed and polished by techniques commonly used in the field. The slabs described above are cut from a block of stone material to the above-mentioned thickness, for example by means of a sawing machine comprising a suitable cutting block. Said cutting block will be described hereinafter with reference to one of its non-limiting exemplary embodiments, illustrated by the appended drawings, in which: Figure 3 shows in perspective, partially in section, a sawing frame; Figure 4 shows in perspective a detail of a cutting block; Figure 5 shows an exploded axonometric view of a detail of the cutting block of Figure 3 ; Figure 6 shows, in a partially sectional top view, a second detail of a cutting block; Figure 7 shows in side view a third detail of a cutting block; Figure 8 shows in a top view the detail of Figure 7; Figure 9 shows in side view a fourth detail of a cutting block; Figures 10 and 11 show, respectively in side view and in a top view, a fifth detail of a cutting block; Figure 12 shows in a top view a detail of the detail of Figure 6 ; Figure 13 shows in perspective a detail of a second embodiment of the invention; Figure 14 shows in a top view the detail of Figure 13 and Figure 15 shows in a top view a detail of a third embodiment of the invention. With reference to the aforesaid drawings, the reference 20 indicates as a whole a sawing machine or sawing frame. Said sawing frame 20 comprises a portal structure 22 within which pendulums 24 can move vertically in a controlled manner (along an axis Y or feed axis) . To the pivoting end of said pendulums 24 there is connected a sawing unit or cutting block 26. Said cutting block 26 is connected to an actuating device, comprising a connecting rod 28 and a crank 30 connected operationally to a reduction motor 32. The actuating device makes it possible to impart to the cutting block 26 a reciprocating or sawing motion (along an axis X or working axis) . Said cutting block 26 is arranged horizontally for sawing an underlying stone block 34 into slabs according to a sawing technique which is known per se (Figure 3) . Said cutting block 26 comprises opposed tension frames or yokes 40 and 41, connected to each other by struts 42 so as to form a framework. In the aperture delimited by said framework there is a plurality of blades 44. The blades 44 are arranged parallel to one another and are placed under tension by means of tie-bars 46 and 47 co-operating with said yokes 40 and 41. In particular, in the yokes 40 and 41 there are longitudinal slots 48. In a first yoke 40 there is provided laterally to said slot 48 a plurality of piston and cylinder devices 50 actuated hydraulically . Said cylinder and piston devices 50 emerge from the yoke 40 outside the framework, constituting a thrust surface or bed. A first said tie-bar, or movable tie-bar 46, is received transversely in the slot 48 of said yoke 40 provided with thrust bed so as to bear with one end, widened into a T- shaped head 52, on said thrust bed, to be urged so as to be drawn out from the framework. In the slot 48 of the opposed yoke 41 a second said tie-bar, or fixed tie-bar 47, is received transversely so as to bear with an insert, or chock 54, received in a seating 56 transverse thereto, against the outer surface of said opposed yoke 41. The ends 58 and 60, within the framework, of said movable tie-bar 46 and fixed tie-bar 47 co-operate with the ends of blades 44 placed side by side with one another, in the manner which will be described in detail hereinafter (Figures 4 and 5) . The coupling ends 58 and 60 of said tie-bars 46 and 47 advantageously have a single connecting arm, or spur 62, 64, between two blades 44 placed beside each other. Said spur 62, 64 has opposed lateral surfaces 63 and 65 for the support of said two blades 44 placed side by side. Said surfaces 63 and 65 are arranged at a predetermined distance (Figures 6 to 12) . In a first embodiment of the invention, each tie-bar 46, 47 has on its sides of the ends 58 and 60 for coupling with the blades 44 two channels with L-shaped profile, arranged opposite each other and constituting lame bearing or incomplete seats 66. In other words, said incomplete seats are open seats, or in yet other words, the single seat 66 has half-bearing coupling surfaces. Said seats 66 are opposite one another and receive the ends of blades 44 placed beside each other. In this first embodiment of the invention, the bar 68 of the tie-bar 46 and 47 has a thickness sufficient for placing under tension two blades 44 placed side by side and capable of withstanding the sawing action. Each spur 62 and 64 is provided with a transverse through hole 70 that can be aligned with a corresponding through hole 72 provided at the coupling end of the blade 44. Said holes 70 and 72 receive a connecting pin 74. Advantageously, said tie-bars 46 and 47 co-operate with plate-like reinforcing members 76 and 78 placed alongside. In other words, beside each movable tie-bar 46 there is a movable reinforcing member 76 and, respectively, beside each fixed tie-bar 46 is provided a fixed reinforcing member 78. Said reinforcing members 76 and 78 are equipped with a spur 80 and 82. Said spur 80 and 82 has opposed lateral surfaces 84 and 86 for the support of the blades 44 placed beside it. Said surfaces 84 and 86 are arranged at a predetermined distance, for example corresponding to the distance between surface 63 and its opposed surface 65 of the spur 62 and 64 of the tie-bar 46 and 47. In yet other words, the spurs 62, 64, 80 and 82 have the same transverse thickness. Said lateral surfaces 84 and 86 co-operate with the lateral surfaces 63 and 65 of the spur of the tie-bar alongside, so as to surround the end of the blade 44 laterally. In this manner, the plate-like reinforcing members 76 and 78 close the incomplete seats 66 of the tie-bars 46, 47. The lateral surface 84, 86 of the spur 80, 82 provided at the end of the reinforcing member 76, 78 constitutes an abutment for the pin 74 for connection of the tie-bar 46 and 47 to the blades 44. In a different embodiment of the invention, the spur 80, 82 of the reinforcing member 76 and 78 has a through hole 100 arranged coaxially with the through hole 70 of the cooperating tie-bar 46 and 47. Said through hole 100 has a diameter smaller than the diameter of the hole 70 of the tie-bar 46, 47. Said reinforcing members 76 and 78 are coupled by pressure to one of the flanks 88 and 90 of the tie-bars 46 and 47. For example, said reinforcing members 76 and 78 are connected to the flank 88 and 90 of the tie-bars 46 and 47 by threaded means 92 screwed into threaded holes 94 provided in the bar 68 of the tie-bars 46 and 47. The head 96 of said threaded means 92 is advantageously countersunk in seats 98 provided in the reinforcing members 76 and 78. Preferably, said seats 98 are conical and receive conical heads 96 of screws 92. To further advantage, each spur 62, 64, 80 and 82 extends from the bar 68 of the tie-bar 46 and 47, as well as of the reinforcing member 76, 78 in the manner of a hammer-head, or in other words of a T-shaped head. For example, the height of said hammer-head corresponds to the height of the blade 44. Said spur 62, 64 and 80, 82 with hammer-head constitutes a warp-preventing guide for the blades 44 placed side by side. The operation of the cutting block for a machine for sawing stone blocks into slabs is described below. With the machine 20 arranged for sawing a new stone block 34, the fixed tie-bar 47 and movable tie-bar 46 are inserted into the slots 48 of the opposed yokes 40, 41 of the cutting block 26. Said tie-bars 46, 47 are previously coupled to the respective plate-like reinforcing members 76, 78. Then, to each pair consisting of a fixed tie-bar 47 and movable tie-bar 46 there is connected the end of two blades 44 placed side by side. This operation is particularly simple. In fact, the coupling end of each blade 44 is inserted into the seat 66 formed between the spur 62, 64 of the tie-bar 46, 47 and the spur 80, 82 of the reinforcing member 76, 78 or, in other words, in the seats 66 provided laterally of the spur 62, 64 of the tie-bar 46, 47. The blades 44 placed side by side are connected to the spur 62, 64 of the tie-bar 46, 47 by the insertion of the pin 74 into the through hole 70 of the tie-bar 46, 47. Said pin 74 is pushed as far as it will go against the lateral surface 86 of the spur 80, 82 of the reinforcing member 76, 78 at the through hole 100. In the case where it is wished to proceed with the sawing of a stone block 34 into thin slabs it is therefore sufficient to bring the lateral surface of a tie-bar 46, 47 alongside the opposed lateral surface of the reinforcing member 76, 78 of the neighbouring tie-bar 46, 47. In this way, the incomplete seat 66, opposite the reinforcing member 76, 78, of each tie-bar 46, 47 is closed by the outer lateral surface 84 of the reinforcing member 76, 78 of the tie-bar 46, 47 alongside. Furthermore, by bringing a reinforcing member 76, 78 alongside the tie-bar 46, 47, the connecting pin 74 is blocked in the working position. With the blades 44 connected to the movable tie-bars 46 and fixed tie-bars 47, by means of the thrust bed 50 a drawing-out action is exerted on the movable tie-bars 46, placing the blades 44 under tension. When the operation of placing the blades 44 under tension is completed it is possible to proceed with the sawing of the stone block 34 . From the above it can be understood that the proposed cutting block for a sawing frame for sawing stone blocks into slabs makes it possible to obtain the sawing of thin slabs. In fact, the minimum distance obtainable between two opposed blades is equal to the thickness of a single spur. Therefore it will be possible to reduce the distance between two opposed blades as far as a value equal to the minimum thickness with which it is possible to construct a spur capable of withstanding the stress necessary for placing the blade under tension and the stress corresponding to the sawing action. A further advantage of the invention lies in the fact that the structure proposed for the cutting block is particularly simple. Moreover, the proposed cutting block is easy to arrange for sawing. The arrangement side by side of the tie-bars avoids the accumulation of the abrasive mixture necessary for sawing, as well as dirt on the cutting block. A further advantage of the invention is due to the fact that by providing a spur of predefined thickness, or having a predefined distance between the lateral bearing surfaces for opposed blades, it is possible to avoid any further device for regulating the distance between the blades such as the known special spacers. In other words, the spur of the cutting block of the invention, besides constituting a connecting element between the tie-bar and the blade, constitutes a spacing member between two opposed blades. Moreover, said spur performs the further fundamental function of warp-preventing guide for the blades placed beside it . Said unction is particularly important during the sawing operation, and in particular during the attack of the blade on the irregular upper surface of the stone block. It is clear that variants and/or additions to what is described and illustrated above may be provided. In a different embodiment of the invention, the flank 102 of the end of each of the movable tie-bars 46 and fixed tie-bars 47 co-operates with the opposed flank 104 of the tie-bar 46, 47 alongside, surrounding the end of the blades 44. In other words, seats are not provided in the tie-bars 46, 47 for the blades 44 (Figure 15) . In a further embodiment of the invention, each tie- bar 46, 47 has a channel with L-shaped profile at the end for connection to the blade 44. Said channel with L- shaped profile constitutes an incomplete attachment seat 106 for the blade 44. In this case the lateral surface 108 of the tie-bar 46, 47 is brought alongside the lateral surface 110 of the contiguous tie-bar 46, 47 and said tie-bars 46, 47 are arranged with the flanks 108, 110 in mutual contact (Figures 13 and 14) . As can be understood from what is described above, the slab of stone material according to the invention makes it possible to satisfy the requirements referred to in the introductory part of the present description, and at the same time to remedy the drawbacks exhibited by the slabs of stone materials of the prior art. Obviously, a person skilled in the art, for the purpose of satisfying contingent and specific requirements, may apply numerous modifications and variants to the slabs of stone material and the method for obtaining them which are described above, all however included within the scope of the invention as defined by the following claims.

Claims: CLAIMS 1. A method for obtaining a reinforced slab of stone material comprising the step of applying at least one sheet (2) of carbon fibre to a face of said slab of stone material . 2. A method for obtaining a reinforced slab of stone material according to claim 1, comprising, in succession, the steps of: a) applying a layer of resin to one of the two faces of said slab; b) applying at least one sheet (2) of carbon fibre to said layer of resin. 3. A method for obtaining a reinforced slab of stone material according to claim 2 , in which steps a) and b) are followed by a step c) of applying sufficient pressure to said sheet (2) of carbon fibre to incorporate said sheet in said layer of resin. 4. A method for obtaining a reinforced slab of stone material according to claim 2 or 3 , in which steps a) , b) and optionally c) are carried out repeatedly on the same slab of stone material . 5. A method for obtaining a reinforced slab of stone material according to any one of claims 1 to 4 , in which said layer of carbon fibre consists of a sheet of carbon fibre fabric. 6. A method for obtaining a reinforced slab of stone material according to any one of claims 2 to 5, in which said resin is an epoxy resin. 7. A method for obtaining a reinforced slab of stone material according to any one of claims 3 to 6, in which step c) is carried out by means of rolling. 8. A method for obtaining a reinforced slab of stone material according to any one of claims 2 to 7, in which the method further comprises a step d) of drying of the resin. 9. A method for obtaining a reinforced slab of stone material according to claim 8, in which said drying takes place in an oven. 10. A method for obtaining a reinforced slab of stone material according to any one of claims 1 to 9 , further comprising the following steps carried out upstream: a') cutting blocks of stone rock into one or more slabs having a thickness of less than 1 cm spaced by a slab having a thickness of more than 1 cm; b 1 ) applying a removable support to a face of each of said slabs having a thickness of less than 1 cm. 11. A method for obtaining a reinforced slab of stone material according to claim 10, in which said blocks of stone rock are cut into groups of 5 slabs having a thickness of less than 1 cm. 12. A method for obtaining a reinforced slab of stone material according to claim 10 or 11, in which said slabs having a thickness of less than 1 cm have a thickness of between 0.3 and 0.7 cm. 13. A method for obtaining a reinforced slab of stone material according to claim 12, in which said slabs have a thickness of about 0.5 cm. 14. A method for obtaining a reinforced slab of stone material according to any one of claims 10 to 13, in which said slab having a thickness of more than 1 cm has a thickness of about 2.5 cm. 15. A method for obtaining a reinforced slab of stone material according to any one of claims 10 to 14, in which said removable support consists of a baking support . 16. A slab (1) of stone material obtainable according to the method described in any one of claims 1 to 15, characterized in that it comprises a sheet (2) of carbon fibre applied to a face of said slab (1) to reinforce it . 17. A slab (1) of stone material according to claim 16, in which said slab consists of a material selected from the group consisting of marble, granite and semi- marble limestones. 18. The use of carbon fibre fabric for strengthening slabs of stone material. 19. A cutting block (26) for a sawing machine (20) for sawing stone blocks (34) into slabs, comprising a pair of opposed yokes (40, 41) for tensioning a plurality of blades (44) by means of tie-bars (46, 47) with spurs, characterized in that said tie-bars (46, 47) which hold the blades (44) have a single spur (62, 64, 80, 82) between two blades (44) placed side by side. 20. A cutting block (26), according to claim 19, characterized in that said spur (62, 64, 80, 82) constitutes a spacing straightedge for the said two blades (44) placed side by side. 21. A cutting block (26), according to claim 20, characterized in that said spur (62, 64, 80, 82) has lateral surfaces (63, 65, 84, 86), for the support of said two blades (44) placed side by side, arranged at a predetermined distance. 22. A cutting block (26), according to claim 19, characterized in that each tie-bar (46, 47) has on its flanks of the end (58, 60) for coupling to the blade (44) two opposed channels with L-shaped profile constituting incomplete seats (66) for said blades (44) placed side by side. 23. A cutting block (26), according to claim 20, characterized in that said tie-bars (46, 47) co-operate with plate-like reinforcing members (76, 78) alongside, provided with a spur (80, 82) . 24. A cutting block (26), according to claim 23, characterized in that said reinforcing members (76, 78) are coupled by pressure to the flanks of the tie-bars (46, 47) . 25. A cutting block (26), according to claim 24, characterized in that said reinforcing members (76, 78) are connected to the flanks (88, 90) of the tie-bars (46, 47) by threaded means (92) screwed into threaded holes (94) provided in the bar (68) of the tie-bars (46, 47) . 26. A cutting block (26), according to claim 25, characterized in that the head (96) of said threaded means (92) is countersunk in seats (98) provided in the reinforcing members (76, 78) . 27. A cutting block (26), according to claim 26, characterized in that said seats (98) are conical and receive conical heads (96) of screws (92) . 28. A cutting block (26), according to claim 19, characterized in that each spur (62, 64, 80, 82) extends from the bar of the tie-bar in the manner of a hammerhead. 29. A cutting block (26) , according to claim 28, characterized in that said spur (62, 64, 80, 82) constitutes a warp-preventing guide for the blades (44) placed side by side. 30. A cutting block (26), according to claim 19, characterized in that each spur (62, 64, 80, 82) is provided with a through hole (70) that can be aligned with a corresponding through hole (72) provided in the coupling end of the blade (44) for receiving a connecting pin (74) . 31. A cutting block (26), according to claims 30 and 23, characterized in that the lateral surface (84, 86) of the spur (80, 82) provided at the end of the plate-like reinforcing member (76, 78) constitutes an abutment for said connecting pin (74) . 32. A cutting block (26), according to claims 30 and 23, characterized in that the spur (80, 82) of the plate-like reinforcing member (76, 78) has a through hole (100) coaxial with the through hole (70) of the cooperating tie-bar (46, 47) and having a smaller diameter. 33. A cutting block (26), according to claim 19, characterized in that the flanks of the end of each of said tie-bars (46, 47) co-operate with the opposed flank of the tie-bar (46, 47) alongside, constituting attachment seats for the ends of the blades (44) . 34. A cutting block (26), according to claim 19, characterized in that said tie-bars (46, 47) are arranged with the flanks in mutual contact . 35. A cutting block (26), according to claim 34, characterized in that each tie-bar (46, 47) has a channel with L-shaped profile which constitutes an incomplete attachment seat for the blade (44) .

Inventors: BRUSADELLI EMILIO, POZZI ALESSANDRO, BRUSADELLI, EMILIO, POZZI, ALESSANDRO
Applicants: BRUSADELLI EMILIO, CALVASINA S P A, POZZI ALESSANDRO, BRUSADELLI, EMILIO, CALVASINA S.P.A., POZZI, ALESSANDRO
Application year: 2000
Main classification: B28D
IPC codes: B27B3, B28D1, C04B41