The present invention regards a method of obtaining a tool, and in particular an abrasive block, particularly for working both natural and artificial stone materials.

The polishing of stone materials, e. g. calcareous or marble stones, is usually achieved by polishing tools, termed blocks in jargon. Such tools usually have a working portion, i.e. that intended to come into direct contact with the material to be worked, which includes a salt, normally a potassium acid oxalate derived from oxalic acid, from which potassium bioxalates or tetraoxalates can be obtained. Such salt is suitable for binding with calcium carbonate, thus forming an insoluble salt, calcium oxalate, which has a very brilliant appearance.

Usually, the starting salt is mixed with natural resins, such as lac, or synthetic resins, such as phenol or polyester resins, so as to obtain blocks that are removably anchorable to a rotating polishing head of a polishing machine.

Such head can operate with a plurality of blocks, e. g. six or more blocks arranged radially thereon.

Potassium acid oxalate, known to be a harmful substance, constitutes a polluting agent for the environment. Considering that at least the part of the block-tool directly anchored on the polishing head or close to the same cannot be fully used for working a stone surface to be polished, at the end of the useful lifetime of the tool it must be removed from the polishing head and disposed of respecting severe safety laws and criteria in handling and destroying the polluting materials. The main object of the present invention is to provide a method for making a new abrasive block tool structure.

Another object of the present invention is to provide an abrasive block tool structure that, once used up to the end of its useful lifetime, does not require being treated as a polluting waste material, which is entirely advantageous with regard to working costs and environmental protection costs.

Another object of the present invention is to provide a new abrasive block structure that can be obtained with competitive costs with respect to the conventional abrasive blocks.

According to a first aspect of the present invention, a method is provided of obtaining a block tool, particularly for working stone materials, comprising the following steps:

- arranging: a) at least one mold member; b) at least one foamable fluid compound selected from the group including epoxy, polyurethane, silicon, polyester and acrylic resins; c) granular material comprising at least one salt of a component selected from the group including oxalic acid and its derivatives; and d) at least one barrier member for the at least one salt, permeable to the foamable fluid compound, such barrier member being engageable with the mold member;

- engaging the at least one barrier member with the at least one mold member, thereby delimiting therein a receiving zone and a foaming zone;

- supplying the at least one foamable fluid compound into the receiving zone in the at least one mold member, and the granular material in the receiving zone or in the foaming zone; and - letting the at least one foamable fluid compound to foam or causing it to foam from the receiving zone to the foaming zone, whereby a portion of the at least one expansible fluid compound flows through the at least one barrier element, thus obtaining a block tool having a connecting portion including the at least one foamed compound, and a working portion comprising both the at least one foamed compound and the at least one salt.

In accordance with a second aspect of the present invention, a block tool support or base is provided, comprising a substantially tubular body delimiting an axial light therein, and at least one barrier member having pores of size ranging from 0.1 mm to 15 mm, the at least one barrier member being anchored to the substantially tubular body thereby intercepting the axial light thereof.

According to a third aspect of the present invention, a tool is provided comprising a connecting portion including at least one foamed compound selected from the group comprising epoxy, polyurethane, silicon, polyester and acrylic resins, and a working portion including granular material comprising at least one salt of a component selected form the group including oxalic acid and its derivatives in mixture with a foamed compound selected from the group comprising epoxy, polyurethane, silicon, polyester and acrylic resins, the working portion and the connecting portion being separated by at least one barrier member permeable to the at least one foamed fluid compound before and/or while being foamed, and impermeable to the at least one salt, the at least one salt being located only in the working portion.

Further aspects and advantages of the present invention will be clearer from the following detailed description of specific embodiments thereof, such description being made with reference to the accompanying drawings, in which: - Figures 1 to 3 are schematic views that illustrate respective steps of a method according to the present invention;

- Figure 4 is a view similar to Figure 3 which illustrates a step of another way of implementing the method in accordance with the present invention;

- Figure 5 is a view similar to Figure 3 which illustrates a step of another way of implementing the method in accordance with the present invention;

- Figures 6 and 7 are respectively plan and side views of a grid or web for implementing a method according to the present invention;

- Figures 8 and 9 are respectively plan and side views of a support or base according to the present invention;

- Figure 10 is a section view taken along the line X-X of Fig. 8;

- Figures 1 1 to 14 are respectively bottom, front, top and side views of a tool obtained with a method according to the present invention;

- Figure 15 is a section view taken along the line XV-XV of Fig. 14;

- Figures 16 and 17 are top and side views of a mold in which several tools were made according to the present invention;

- Figure 18 is a section view taken along the line XVII I-XVI 11 of Fig. 16;

- Figures 19 and 20 are bottom and side views of a mold element in which several tools were made according to the present invention;

- Figure 21 is a section view taken along the line XXI-XXI of Fig. 19;

- Figures 22 and 23 are respectively plan and side schematic views of a plant for implementing a method according to the present invention.

In the accompanying drawings, equivalent parts or components were marked with the same reference numerals. The present invention regards a method of obtaining a tool for working stone materials, according to which the following are arranged:

- one or more mold members 1 ;

- at least one foamable fluid compound selected from the group including epoxy resins, such as the resins known as EPOXY FOAM + MR20H produced by

Tenax S.p.A. (Volargne - Verona - Italy) or YD1 106D250/TH7161 , YD1106D350/TH7161 , YD1 106D400/TH7161 produced by ADITYA BIRLA CHEMICALS (Thailand), polyurethane resins, such as resins known as DAGOXYL ET O 200 GP + DAGOSIS MH 6040ML produced by Dagos s.r.l. (Milan - Italy), silicon resins, polyester resins and acrylic resins, e. g. foamable by means of foaming agents, such as the resins known as EXPANCEL produced by Akzo Nobel nv (Amsterdam - Netherlands);

- a granular material comprising at least one salt selected from the group including oxalic acid and derivatives thereof, such as potassium acid oxalate, potassium acid bioxalate, potassium acid tetraoxalate, and acetosella salts, preferably a potassium acid oxalate; and

- at least one barrier member for the salt, permeable to the foamable fluid compound. Preferably, the pores of the barrier member range in size from 0.1 to 15 mm. Thus, the barrier member prevents the passage of the salt granules and is impermeable thereto, but allows the passage of the foamable fluid compound by being permeable thereto.

Then, the foamable fluid compound and the granular material are supplied into the mold member(s), and the barrier member is engaged with the mold element 1 before or after such supply so as to delimit a receiving zone ZC and a foaming zone ZE. According to the method in accordance with the present invention, the foamable fluid compound is supplied into the receiving zone ZC, while the granular material is housed in the receiving zone ZC or in the foaming zone ZE.

After having carried out the above-described steps, the foamable fluid compound is allowed to expand or caused to expand from the receiving zone ZC to the foaming zone ZE, so that a portion of the foamable fluid compound passes through the barrier member, thus obtaining a tool 4 equipped with a working portion 4a including the salt granules in mixture with part of the expanded fluid compound, and a connecting portion 4b including the other part or portion of the fluid compound now in expanded state.

Advantageously, according to the method in accordance with the present invention, the supply of the foamable fluid compound is carried out before the barrier member is engaged with the mold member 1. Still more advantageously, also the supply of the granular material is carried out before the barrier member is engaged with the mold member 1.

Preferably, moreover, the granular material and the foamable fluid compound are supplied together in mixture into the mold element(s).

According to the present invention, the foamable fluid compound is supplied by casting in the mold element 1.

Salts that can be used for carrying out a method or a tool according to the present invention are for example the salts known as "Potassium Tetraoxalate type B", "Potassium Tetraoxalate type C", "Potassium Tetraoxalate type UV, all produced and sold by Connects Chemicals Italia s.r.l. of Vimercate (Milan).

Advantageously, the granular material includes, in addition to the above- indicated salt granules, also one or more mineral or metal compounds selected from the group including talc, calcium silicate, calcium carbonate, magnesium carbonate, magnesium oxide, aluminum oxide, tin oxide, cerium oxide, zirconium oxide, and metal materials such as bronze, copper, tin, silver and lead.

With reference to Figures 1 to 3, respective steps are illustrated of a method in accordance with the present invention, according to which, after having arranged a mold member 1 , a mixture of granular material is supplied therein, including a salt as indicated above and a foamable fluid compound. Then, (possibly after a step of leveling the mixture supplied in the mold member) a barrier member, such as a grid or web 2a, is engaged with the mold member 1 , thereby delimiting a receiving zone ZC.

The mold member 1 can for example include a bottom wall 1 a and a side wall 1 b rising from the bottom wall 1 a, thereby delimiting a receiving cavity. At its top, the side wall 1 b has a flanged terminal outwardly projecting section 1 c, e. g. substantially parallel with the bottom wall 1 a, and delimits an external abutment shoulder. At a predetermined distance from the flanged terminal section 1 c, an external lower shoulder 1 d is preferably provided.

According to the embodiment illustrated in Figs. 1 to 3, in addition to the above-indicated members (mold member, foamable fluid compound, granules and barrier member), a counter-mold member 5 is also arranged.

The counter-mold member 5 includes, for example, a tubular body provided with a first section delimiting an axial light with constant cross section 5a and then a second section 5b delimiting an axial light with cross section that increases moving away from the first section 5a.

The first section 5a also has slightly lower section and greater extension than the flanged terminal section 1c of the mold member 1 , so that the first section 5b of the counter-mold member 5 can be perfectly inserted in the mold member 1 and abutted against the shoulder 1 d.

In order to achieve the method according to the present invention, a mixture of foamable fluid compound and granular material is supplied into the mold element 1 , the grid or web 2a is arranged on the external lower shoulder 1 d of the mold member 1 , and then the counter-mold member 5 is abutted against the grid or web 2a, so as to removably lock the grid or web 2a in position between the mold member 1 and the counter-mold member 5.

The granules and the fluid compound will then be housed in the receiving zone ZC, delimited between the mold member and the grid or web.

Preferably, moreover, the position maintenance of the counter-mold member 5 can for example be obtained by placing a thrust or pressure element thereon, on the side of the counter-mold 5 opposite the mold member 1. Such thrust or pressure element could be a sheet 6 or the like.

At this point, foaming of the foamable fluid compound is caused, e. g. via heating. During such foaming, the fluid compound will partly pass through the grid or web 2a so as to penetrate into an foaming zone ZE, which is delimited by the grid or net 2a, counter-mold member 5 and pressure member 6.

When the foamable fluid compound hardens (e. g. following a cooling thereof), the mold member 1 and the counter-mold member 5 are removed and the tool is extracted.

With one such method, one will obtain a tool 4 provided with a connecting portion 4b (e. g. to a mandrel of a machine tool), which comprises part or a portion of the foamed fluid, selected from the group comprising epoxy, polyurethane, silicon, polyester and acrylic resins, e. g. foamable by the action of foaming agents, and a working portion 4a including granular materials comprising at least one salt of a component selected form the group including oxalic acid and its derivatives, such as potassium acid oxalate, potassium acid bioxalate, potassium acid tetraoxalate, and acetosella salts, in mixture with the other part or portion of the expanded fluid compound. Between the working portion 4a and the connecting portion 4b there is the barrier member, e. g. a grid or web 2a. In one such tool, the salt is only in the working portion 4a. In one such tool, the barrier member is permeable to the foam fluid compound before and/or during the foaming thereof and is impermeable to the salt.

Preferably, the mold member and the counter-mold member are made of a material, e. g. PVC, that the fluid compound does not adhere to.

In Figure 4, an alternative step is illustrated with respect to that of Fig. 3. Here, after having arranged the barrier member, e. g. a grid or web 2a, on the shoulder 18, a support or base element 7 for a tool is arranged, such as a block tool for the polishing of stone materials. The support element includes a tubular side wall, which comprises a first section 7a delimiting an axial light with substantially constant cross-section and then a second section 7b that is flared or delimiting an axial light with cross-section that increases moving away from the first section 7a.

In order to achieve a method according to the present invention, one proceeds as described above with reference to Figures 1 and 2, and subsequently in place of the counter-mold element 5, the support or base 7 is arranged. With one such method, a tool is obtained in which the connecting part 4b is housed and anchored to the machine tool anchoring support or base 7. The support or base will preferably be made of a material on which the fluid compound adheres, e. g. polystyrene for molding (PST) or polyurethane for molding (PU).

With reference to Figure 5, an alternative step is illustrated with respect to Fig. 3, which is achieved by means of a support 70 (see Figs. 8 - 10).

The support or base 70 comprises a substantially tubular body delimiting an axial tunnel, and at least one barrier member intended to intercept the axial light.

The barrier member is anchored, e. g. glued to the support or base, or preferably the barrier member includes a porous wall made integrally with the base. In such case, the support 70 can comprise a porous base wall 70c from which one or more side walls rise, which comprise a first section 70a delimiting an axial light with substantially constant cross-section and then a second section 70b that is flared or delimiting an axial light with cross-section that increases moving away from the first section 70a.

In order to achieve a method according to Figure 5 with a support 70, a mixture of foamable fluid compound and granular material is supplied into the mold member 1 , then the support or base 70 is abutted against the mold member, in particular with the porous wall 70c close to and partly in abutment against the shoulder 1d.

Preferably, moreover, the position maintenance of the support 70 in abutment against the mold member 1 can be ensured as described above with reference to the counter-mold member 5, hence with a sheet 6 or the like means.

As will be understood, one such mold can be provided for such that several impressions are delimited, in order to allow making several tools simultaneously. With particular reference to Figs. 16 to 18, a mold is illustrated intended to make six tools simultaneously, which includes six mold elements 1 anchored together, e.g. made of a single piece.

In Figures 19 to 21 , a counter-mold is illustrated that can be used with the mold member of Figs. 16-18, and includes six counter-mold members 5 that are anchored together, e.g. made of a single piece.

With reference to Figs. 22 and 23, a plant 10 is illustrated for carrying out a method according to the present invention. Such plant includes:

- a first station 12 for supplying one or more mold members 1 ;

- a station 13 for delivering the mixture of foamable fluid compound and salt granules into the mold member(s) 1 ;

- a station 14 for applying a grid, web or porous wall, so as to engage it with the mold member(s);

- a station 15 for drawing one or more finished tools.

The plant also preferably includes a conveyor belt 11 for conveying the mold members along the various stations of the plant.

A station 17 can be provided for applying a counter-mold member or members 5 or a support or base 7 atop and in abutment against respective mold member(s) 1.

Possibly, the plant also comprises a station 18 for leveling the mixture in the mold member(s), and a heating station 19 in which foaming of the foamable fluid compound is caused.

As will be understood, with a method according to the present invention, a tool is obtained having a connecting portion that only includes the non-polluting compound, the salt granules only being provided for in the working portion. After such tool has been used, and its working portion is fully worn, the tool can be disposed of without high costs, since the part of the tool to be disposed only comprises non-polluting compounds.

The above-described method is susceptible to numerous modifications and variants within the protection scope defined by the claims.

Thus, for example, it can be provided that the salt granules and foamable fluid compound are separately supplied. In addition, for example, it can be provided that the foamable fluid compound is applied in the receiving zone, and the granules in the expansion zone, and subsequently the foamable fluid compound is allowed or caused to foam from the receiving zone to the expansion zone, thus obtaining the dispersion of the granules in the foamed fluid compound portion in the foaming zone.

The barrier member can be obtained from a roll of porous material, which is unrolled on top of the mold member(s) and cut to the desired size, at the start or during the production cycle of the tool.

The method described above is susceptible to numerous modifications and variants within the protection scope defined by the claims.