Technical Field

[0001] The present invention generally finds application in the field of stone working, i.e. working on stone materials such as marble, granite, onyx and the like, and particularly relates to a method of enhanced resin-reinforcement of a block of one of these materials, having cracks and/or surface defects or at different depths.

Background Art

[0002] In the field of stone working, quarry blocks are known to exhibit a large and increasing amount of natural stone defects, namely surface or internal cracks at different depths, possibly having a“heart” shape, due to the poor availability of quarrying sites and the environmental and social obstacles to protection.

[0003] In view of obviating this serious drawback, resin-reinforcement methods have been long known for consolidating the blocks and making them ready for subsequent cutting into slabs, without exposing them to fracture or crumbling.

[0004] Furthermore, defective blocks have always caused a safety issue in the working cycle to convert them into slabs and in slab working processes.

[0005] Prior art resin-reinforcement methods included forming a wooden formwork that enclosed the block and creating a gap between the formwork and the block surface, and later pouring a curing resin into the gap to spread the resin into the interstices of the block.

[0006] Typically, the resin is mixed with catalysts to accelerate curing once it has penetrated the defects.

[0007] Furthermore, the method includes a step of introducing the block enclosed in the formwork into a hermetically sealed environment, such as an autoclave, whose pressure is decreased and possibly later increased from atmospheric pressure to urge the fluid resin into the cracks or defects before resin curing.

[0008] A first drawback of this prior art method is that the provision of a formwork entails heavy labor and material requirements and a resulting increase of repair costs.

[0009] A further drawback is that the outer surface of the block often has an irregular shape, whereby a gap having a considerable volume and a variable thickness is formed between the inner walls of the formwork and the outer surface of the block.

[0010] Since this gap must be entirely filled to ensure that the defects or cracks of the block will be filled up, the use of a formwork entails the consumption of large amounts of resin, much larger than those strictly required for block repair.

[0011 ] A further drawback is that this method requires plants with dedicated workstations to ensure optimized implementation.

[0012] In an attempt to at least partially obviate these drawbacks, methods for resin-reinforcement of stone slabs have been developed, which use flexible materials conforming with the irregular shape of the block.

[0013] W02005/077645 discloses a method of resin-reinforcement of marble blocks which includes applying a drainage layer to at least the side walls of the block and a later step of introducing the block into a bag formed from a sheet of flexible waterproof material.

[0014] The bag is connected to a vacuum pump and has connectors for a resin to be injected by a mixing and injection apparatus. Then, vacuum is maintained in the bag until the resin is fully cured.

[0015] One drawback of this known method consists in that the application of the drainage layer on the walls of the structural member is a time-consuming and laborious operation, which requires considerable labor, with a corresponding increase of process costs.

[0016] Furthermore, once the resin has cured, the flexible sheet may adhere on the drainage layer thereby preventing its removal at the end of the process and before cutting the block into slabs. The plastic sheet that adheres to the drainage layer must be necessarily removed before sawing to avoid problems during sawing and any damage to the cutting machine.

Technical Problem

[0017] In view of the state of the art, the technical problem addressed by the present invention is to provide a simpler and more effective method of resin- reinforcement of blocks, while reducing process times and the amount of resin to be used and enhancing resin-reinforcement.

Disclosure of the invention

[0018] The object of the present invention is to obviate the above drawback, by providing a method of enhanced resin-reinforcement of a stone material that is highly efficient and relatively cost-effective.

[0019] A particular object of the present invention is to provide a method as described hereinbefore that can be easily implemented and reduces the overall amount of resin to be used in the process.

[0020] A further object of the present invention is to reduce the steps of the resin-reinforcement method, by avoiding the application of drainage or intermediate layers.

[0021] Another object of the present invention is to provide a method as described hereinbefore that can consolidate blocks irrespective of their shape and size.

[0022] Yet another object of the present invention is to provide a method as described hereinbefore that can consolidate a block having both defects both at the surface and at a greater depth and irrespective of defect types.

[0023] These and other objects, as more clearly explained hereinafter, are fulfilled by a method of enhanced resin-reinforcement of a block of a stone material, such as marble, granite, onyx, having cracks and/or shallow or deep defects, as defined in claim 1 .

[0024] In a preferred embodiment, the process comprises the steps of a) laying a sheet of flexible waterproof plastic material on a base that rests on the ground and placing a block to be resin-reinforced on the sheet, b) applying a plurality of spacer members to one or more walls of the block c) folding the sheet on the walls of the block to thereby form a container with a gap from the outer surface of the block formed by the spacer members and d) hermetically sealing the container and applying at least one first connector on its surface.

[0025] In a preferred embodiment, the method includes the steps of: e) connecting the at least one first connector to a vacuum pump via first pipes to create a vacuum in the container, f) introducing a resin in the liquid or pasty state into the container via second pipes connected thereto through a second connector, differing from the first connector, to fill the gap, g) maintaining the vacuum in the container for a predetermined time until the resin is at least partially cured and h) disconnecting the first and second pipes from the container and removing the resin-reinforced block from the container.

[0026] In a peculiar aspect of the invention, the step of b) applying the spacer members to one or more walls of the block is followed by a step of i) helically winding a reinforcing belt made of a flexible sheet material on the spacer members around the walls of the block. The reinforcing belt is pulled to exert a radial inward compression force on the block.

[0027] With this succession of steps, resin-reinforcement may be carried out in a simple manner, and the overall amount of resin to be used in the method may be reduced.

[0028] Advantageously, the base material of the belt is selected from the group comprising synthetic fabric, polyester, leather or other resin- impermeable, non-draining material.

[0029] Due to this feature, the belt may be applied to the block and the liquid or pasty resin may penetrate the cracks and/or shallow or deep defects without sticking to the plastic sheet of the container and the sheet may be reused for resin-reinforcement of further blocks.

[0030] Advantageous embodiments of the invention are obtained in accordance with the dependent claims.

Brief description of the drawings

[0031] Further features and advantages of the invention will be more apparent from the detailed description of a preferred, non-exclusive embodiment of a method of enhanced resin-reinforcement of a stone block according to the invention, which is described as a non-limiting example with the help of the annexed drawings, in which:

FIG. 1 is a block diagram of the resin-reinforcement method of the invention; FIGS. 2 and 3 are schematic perspective views of first and second steps of the inventive method;

FIGS. 4 and 5 schematically show a side view and a perspective view of additional steps of the inventive method;

FIG. 6 is a schematic top view of Fig. 5.

Detailed description of a preferred exemplary embodiment

[0032] Particularly referring to the above figures, there is shown a method of enhanced resin-reinforcement of a block 1 of a stone material, such as marble, granite, onyx and the like having surface cracks D and/or defects at different depths.

[0033] As used hereinafter, the term “resin-reinforcement” is intended to designate the process for applying a resin layer on the surface of a block or an article made of stone material to penetrate its surface defects by coating, injection or suction, in order to consolidate the base material before any further handling and cutting into slabs.

[0034] In a preferred embodiment of the invention, as shown in FIG. 2, the method comprises a step of a) laying a sheet 2 of flexible waterproof plastic material on a base 3 resting on the ground and placing a block 1 to be resin- reinforced on the sheet 2.

[0035] The plastic material of the sheet 2 may preferably be transparent and selected from the group of plastic materials including, as a non-limiting example, nylon, polyethylene, silicone or silicone-backed fabric. The base 3 may comprise a suitably reinforced wooden pallet or a rotating metal support adapted to facilitate the subsequent steps of the method.

[0036] Conveniently, the block 1 may be previously washed, dried and possibly pre-heated before the step of a) placing the block 1 on the sheet of plastic material 2.

[0037] Preferably, the sheet 2 may be placed on the base 3 with the interposition of a cushion layer 3' made of a soft material, adapted to protect the sheet 2 from cuts and ruptures.

[0038] Such cushion layer 3' may comprise a fabric of predetermined thickness, made of fibers of natural or synthetic material, possibly associated with suitable spacers to support the weight of the block 1 .

[0039] As shown in FIGS. 2 and 4, the method includes a step of b) applying a plurality of spacer members (4) to one or more walls of the block 1 and a step of c) folding the sheet 2 on the walls of the block 1 to form a container 5 with a gap 6 from the outer surface of the block 1 formed by the spacer members 4.

[0040] As used hereinafter, the term“spacer” shall be intended to designate any member adapted to be applied to a surface to prevent a sheet or sheet member that lies on such surface from entirely adhering to the surface.

[0041] Advantageously, the spacer members 4 may be listels or bars of a material selected from the group comprising wood, plastic, iron or linear shims made of a rigid or partially rigid material.

[0042] Preferably, each spacer member 4 may have a thin and elongated strip shape or a substantially elongate shape with a cross section selected from the group comprising squares, rectangles or circles.

[0043] Of course, each spacer member 4 may have a short and squat shape or other irregular shapes other from those described above.

[0044] Furthermore, the above described shapes are only given by way of example and may be suitably changed according to the types of defects D in the block 1 and the desired repair level, without departure from the scope of the present invention.

[0045] In a first embodiment of the invention, as shown in FIG. 2, the spacer members 4 may be only applied to the block 1 at the areas with the defects D, to avoid unnecessary operations on the non-defective parts.

[0046] In a second embodiment of the invention, the plurality of spacer members 4 may be applied in a regular pattern on the side walls of the block 1 to be resin-reinforced, to efficiently facilitate repair of the block 1 and impart resistance thereto during cutting.

[0047] For this purpose, the step b) of applying the plurality of members 4 may be carried out by gluing the spacer members 4 with silicone or another equivalent adhesive.

[0048] As shown in FIGS. 4 and 5, the method includes the step d) hermetically sealing the container 5 and applying at least one first connector 7 on its outer surface and e) connecting the at least one first connector to a vacuum pump 12 via first pipes 8 for creating a vacuum in the container 5, as shown in FIG. 4.

[0049] As is known per se, the step of e) creating vacuum in the container 5 may be obtained by means of a pump or an autoclave 12, adapted to extract the air in the container 5 and in the defects D of the block 1 , to thereby provide a vacuum ranging from -0.9 bar to -2 bar, preferably of -0.5 bar, in the container 5.

[0050] As shown in FIGS. 1 , 4 and 5, the method comprises a step of f) introducing a resin R in the liquid or pasty state into the container 5 via second pipes 9 connected thereto through at least one second connector 10, differing from the first connector 7, to fill the gap 6.

[0051] As is known per se, the resin R may be selected from the group comprising epoxy, polyurethane, polyester, thermoplastic and water resins or a combination thereof.

[0052] This step of f) introducing the resin R may be carried out by connecting the second pipes 9 to a suitably sized container, containing the resin R mixed with a catalyst of a known type.

[0053] As shown in FIG. 4, the resin R mixed with the catalyst may be urged into the gap 6 due to the vacuum created by the vacuum pump 12.

[0054] Thus, in addition to extracting the air in the container 5, the pump will allow the resin R mixed with the catalyst to flow through the second pipes 9, enter the gap 6 and be drawn into the defects D of the block 1 .

[0055] In a preferred embodiment, the flexible waterproof sheet 2 may be made of silicone or silicone-backed fabric to facilitate reuse thereof for other stone blocks 1 .

[0056] In this embodiment, the sheet 2 may be bag-shaped, possibly with a removable or zipper sealed cover 5' to form the container 5 in the sealing step d).

[0057] In this embodiment, the inner surface of the sheet 2 that contacts the block 1 to be resin-reinforced may be coated with a PTFE-based release paint to prevent the resin R from adhering to the sheet 2 so that the latter can be reused for resin-reinforcement of other stone blocks 1 .

[0058] This embodiment can also avoid the use of the cushion layer 3' between the base 3 and the block 1 and allows the container 5 to be reused for resin-reinforcement of other blocks 1 .

[0059] This is because silicone is a material with high non-stick properties and can be easily detached from the resin R, without leaving residues on the sheet 2.

[0060] Once the vacuum has been created, the block 1 in the container 5 undergoes a step of g) maintaining the vacuum in the container 5 for a predetermined time t until the resin R is at least partially cured, as shown in FIG. 5.

[0061] The predetermined time t of the maintaining step g) may vary according to the material of the resin R, the type of catalyst and the shape and size of the block to be resin-reinforced 1 .

[0062] By way of example, a predetermined vacuum maintaining time t of about 18 hours will be sufficient for resin-reinforcement of a marble block approximately having a cube shape of side 2.5m.

[0063] Finally, a step is provided of h) disconnecting the first 8 and second pipes 9 from the container 5 and removing the resin-reinforced block 1 from the container 5 for later processing of the block 1 in safe conditions.

[0064] Of course, both placement of the block 1 on the base 3 in step a) and removal of the block 1 from the container 5 in step h) may be carried out by any lifting and transport means, for example a crane or a lift truck, not shown.

[0065] In a peculiar aspect of the invention, as shown in FIG. 3, the step of b) applying the spacer members 4 to one or more walls of the block 1 is followed by a step of i) helically winding a reinforcing belt 1 1 made of a flexible sheet material on the spacer members 4 around the walls of the block 1 . Furthermore, the reinforcing belt 1 1 is pulled T to exert a radial inward compression force on the block 1 .

[0066] The belt 1 1 may be subjected to a pull force T ranging from 1000 and 5000 N.

[0067] As used hereinbelow, the term "belt" is intended to designate an elongate member made of a flexible sheet material and having a rectangular plan shape with a width considerably smaller than its total length, i.e. with an aspect ratio ranging from 1 :50 to 1 :200, which is adapted to impart considerable tensile strength with limited elongation.

[0068] Advantageously, the base material of the reinforcing belt 1 1 may be selected from fabric-like sheet materials made of reinforced synthetic fibers, polypropylene, polyester, leather, aramid fiber or other material that is impermeable to the resin R and has no draining properties, with a maximum tensile strength ranging from 2000 to 30000 N.

[0069] Conveniently, the belt 1 1 has an initial portion 1 1 ' that is stably attached to the block 1 , for example by gluing with silicone or an equivalent adhesive, or by means of hooks and other fasteners and an end portion 1 1” that is helically wound around the lateral wall of the block 1 .

[0070] The end portion 1 1” of the belt 1 1 will be pulled by the pull force T, e.g. by means of clamps, pawls or tension levers.

[0071] Furthermore, the reinforcing belt 1 1 may be non-continuously wrapped around the walls of the block 1 with a gap being left between its edges at each turn.

[0072] Conveniently, during the step of e) creating the vacuum, the vacuum in the container 5 may exert an inwardly-directed compression force on the reinforcing belt 1 1 , to thereby adhere it to the areas of the outer surface of the block 1 without the spacer members 4.

[0073] By this arrangement, during the step of f) introducing, the resin R may infiltrate the gap 6 formed between the belt 1 1 and the block 1 provided with the spacer members 4.

[0074] Furthermore, in the second embodiment in which the spacer members 4 are only applied in correspondence of the defects D, the resin R held by the reinforcing belt 1 1 , may only infiltrate the defects D, without altering or interacting with the parts of the block 1 that have no defects D, as shown in FIG. 6.

[0075] It will be appreciated that the particular combination of characteristics of the reinforcing belt 1 1 and of the enhanced resin-reinforcement method of the invention can reduce the overall amount of resin R, irrespective of the shape and size of the block to be resin-reinforced 1 .

[0076] In addition, the method of the invention avoids the use of additional drainage layers.

[0077] It will be apparent from the foregoing that the method of enhanced resin-reinforcement of a stone block fulfills the intended objects, and can namely provide a simple and more effective resin-reinforcement of the blocks, in addition to reducing manufacturing times and the amount of resin in use.

[0078] The method of resin-reinforcement of stone blocks according to the invention is susceptible of a number of changes and variants, within the inventive concept disclosed in the appended claims.

[0079] While the method has been described with particular reference to the accompanying figures, the numerals referred to in the disclosure and claims are only used for the sake of a better intelligibility of the invention and shall not be intended to limit the claimed scope in any manner.

[0080] Reference herein to "one embodiment" or "the embodiment" or "some embodiments" indicates that a particular characteristic, structure or member that is being described is included in at least one embodiment of the inventive subject matter.

[0081] Furthermore, the particular characteristics, structures or members may be combined together in any suitable manner to provide one or more embodiments.

Industrial Applicability

[0082] The present invention may find application in industry, because it can be produced on an industrial scale in factories of the stone or stone-like working industry.