The present invention relates to a tool, particularly a block tool for surface polishing or lapping operations e. g. for polishing or lapping flooring and/or coating tiles made of stone, ceramic and the like materials, as well as a process for obtaining it.

Methods of polishing flat and not-flat surfaces, in particular ceramic tiles, have already been proposed which are mainly carried out by means of block or plug tools of various types, such as having blocks glued onto rubber supports having a hardness in a given range of shore degrees. Block tools are usually obtained by a moulding process, which initially involves prearranging a press or a mould, usually made of aluminum, formed with a plurality of cavities, each of which corresponds to the configuration of a block. A solution or mixture containing one or more thermosetting resins and an abrasive material dispersed therein, is then poured into each cavity of the mould and a layer of "Velcro"™ is laid on the upper surface of the mould, thereby covering the cavities loaded with the mixture. The press or mould is then closed and heated for about 15-30 minutes at a temperature between about 1 10-180°C. This causes a small portion of the abrasive solution at first, partly to expand or migrate as a consequence of the expansion into the Velcro layer and, subsequently, to harden, thus obtaining a firm anchoring of the newly formed blocks to the Velcro layer.

At this point, the moulded elements or blocks are extracted from the mould, after which the free face of Velcro (i. e. the face opposite to the blocks) is glued to a rubber plate. The whole assembly is then subjected to a die-cutting operation and, finally, a support, still made of rubber, but with rather low shore hardness, can be glued onto the rubber plate.

Such a solution has proved to be advantageous, as the layer of Velcro firmly holds the blocks together during the gluing steps, whereas the rubber plate and the rubber support give the tool a desired flexibility during the work step.

However, in a tool obtained with such a method, Velcro is fully impregnated by the abrasive solution and then, after curing of the resin or resins, the layer of Velcro becomes rigid, and thus it is necessary to use rather soft rubber plates. On the other hand, the use of highly soft rubber plates could result in a drawback, as this is detrimental to the tool toughness in that tear or detachment of the blocks glued to the rubber can occur during the polishing operations.

The reliability of operation of a tool obtained according to the state of the art is then based on more or less good features of the adhesive, usually an (cyano acrylates-based) acrylic glue, which, especially in the presence of water, becomes deteriorated, thereby jeopardizing the stability and integrity of the tool.

To solve this problem, some solutions have been proposed, such as that constituting the subject-matter of Italian patent application no. VR2008A000130, in the name of the applicant of the present patent application, wherein each block is inserted and anchored, e. g. by means of snap-fitting connection, to the free end of a respective flexible lug extending from a base portion of the tool. With such a solution gluing is avoided, but the blocks can bump against, and obstruct, each other, which hampers compression and stretching movements of the flexible lugs bearing the blocks, which results in a poor reactivity.

Another proposed solution, which is the subject-matter of the Italian patent application no. VR2009A000200 still in the name of the applicant of the present patent application, provides the use of a rigid mask bound to a base portion of the tool and intended to mechanically retain the blocks in position so as to prevent them from coming off. Such a solution involves rather complex production and assembly processes also because, among the other things, a suitably shaped mask should be provided and fastened to the base of the tool while maintaining in position the blocks.

AT379100 instead teaches a method for obtaining grinding wheels, according to which, a layer of a grinding mixture is poured into a mould, whereupon a foil lined with a reinforcing tissue is inserted. Then, second layer of grinding mixture is poured on the foil, and a second foil may be placed thereon. The procedure is repeated until a grinding wheel blank having the desired number of grinding layers, foils, and reinforcing tissues is obtained. At that point, the mould is closed, and foils, reinforcing tissue, and grinding layers are compressed to obtain a grinding wheel having the desired dimensions.

The main object of the present invention is to provide an abrasive tool or block for operations such as polishing and lapping of various materials, which tool, in addition to a high working efficiency, also has optimal flexibility of use with no risk of detachment of the abrasive part from its support.

Another object of the present invention is to provide a process for obtaining an abrasive tool or block having an abrasive or cutting portion and a support or socket portion simple and cost-effective to produce.

Another object of the present invention is to provide a process for obtaining an abrasive tool or block, which does not require any gluing operation, apart from possible gluing for anchoring the abrasive portion of the tool onto a support or socket. According to a first aspect of the present invention, a tool for working material surfaces is provided, having a support base, an abrasive or cutting portion constrained to the support base and obtained from an abrasive solution or mixture, the abrasive or cutting portion comprising a connection portion and a work portion, the tool further comprising a vibration damping element having at least one through opening formed therein, through which part of the abrasive solution or mixture extends from the work portion until it reaches the support base, thereby constraining the work portion to the support base with interposition of the vibration damping element.

Advantageously, the support base is made of an impregnatable layer or fabric, and more advantageously the support base is made of Velcro.

According to another aspect of the present invention a method of obtaining a tool in accordance with the present invention is provided, comprising the following steps:

- feeding an abrasive solution or mixture into at least one cavity of a mould;

- arranging on the mould a vibration damping element in which at least one through opening is formed, whereby the at least one opening is provided at each cavity of the mould;

- laying a support base, such as Velcro, on the vibration damping element; - closing the mould and causing a partial migration or expansion of a portion of the abrasive solution or mixture throughout the at least one opening to impregnate the support base;

- leaving the abrasive solution or mixture to harden or solidify or causing it to harden or solidify, thereby obtaining at least one tool; and

- removing the at least one tool from the mould. According to a further aspect of the present invention a method of obtaining a tool in accordance with the present invention is provided, comprising the following steps:

- arranging a support base on a counter-mould;

- arranging a vibration damping element, in which at least one through opening is formed, on the support base;

- closing the counter-mould against a mould element, at least one cavity being delimited between the counter-mould and the mould;

- supplying an abrasive solution or mixture into the at least one cavity, whereby causing the abrasive solution or mixture partly to cross the at least one opening to impregnate the support base;

- leaving the abrasive solution or mixture to harden or solidify or causing it to harden or solidify, thereby obtaining at least one tool; and

- moving the counter-mould and mould away from one another and removing the at least one tool.

Further aspects and advantages of the present invention will be clearer from the following detailed description of specific embodiments thereof, the description being made with reference to the accompanying drawings, in which:

- Figure 1 is a cross-sectional view of a tool according to the present invention;

- Figures 2 and 3 are an exploded and cut away slightly from above perspective views, respectively, of a complete tool according to the present invention; - Figures 4 to 8, 10 and 12 are perspective views, slightly from above, showing respective operations in sequence for the production of a tool according to Figures 1 to 3;

- Figures 9 and 1 1 are views on an enlarged scale of a detail of Figures 8 and 10, respectively;

- Figure 13 is a view on an enlarged scale of a detail of a step of another method according to the present invention; and

- Figure 14 is a perspective view, slightly from above, of a schematic plant for the production of a tool according to the present invention.

In the drawings, equivalent or similar parts or components are marked with the same reference numerals.

With reference first to Figures 1 to 3, a tool according to the present invention is shown for working (polishing or lapping) surfaces of materials, particularly stony or ceramic materials, which has an abrasive or cutting portion 2 comprising an attachment portion 2a and a work portion 2b, both obtained from a hardened solution or mixture 4 of a resin or resins and a suitable granular abrasive material.

The tool also includes two reinforcing layers: a first reinforcement or stiffening layer or support base 3 anchored to the base portion and made, for example of "Velcro"™, and a second reinforcement layer including a vibration damping element 5, e. g. a rubber plate, in which one or more through openings 5a are formed, through which portions of the hardened or solidified abrasive mixture 4 extend to reach the support base (e. g. a Velcro layer) 3, thereby constraining or making the work portion 2b and the support base 3 integral with one another, but with the interposition of the vibration damping element 5. As a matter of fact, the abrasive portion 2 embeds the two reinforcement layers (Fig. 1 ). Preferably, the two reinforcement layers 3 and 5 are embedded in the attachment portion 2a of the abrasive portion 2.

The vibration damping element 5 is buried in the hardened or solidified abrasive mixture and reduces its continuity, thereby providing it with a desired flexibility.

Preferably, the work portion 2b is shaped as a block or includes a plurality of blocks 2c, and the damping vibration element 5 is formed with one or more through openings or holes 5a at each block 2c, in such a way as the hardened or solidified abrasive solution or mixture 4 of each block 2c extends throughout a respective opening 5a from the work portion 2b to the support base 3.

Preferably, in a tool according to the present invention, the hardened abrasive solution or mixture impregnates the first reinforcement layer or support base 3 only at the through opening/s 5a formed in the damping vibration element 5, so that the first reinforcement layer 3 is not entirely impregnated by the abrasive solution or mixture 4, and thus it is not fully rigid and ensures a firm support for the work portion 2b anyway.

The tool 1 according to the present invention further comprises, if desired, a connection plate 6, preferably made of rubber having a very low shore hardness designed to be fixed, e. g. by gluing, atop the attachment portion 2a, i. e. opposite to the work portion 2b, and an actual socket 7 that can be fixed, e. g. by a suitable adhesive, to the rubber connection plate 6.

The tool 1 is designed to be connected to the rotating work head of a polishing machine by engagement and tightening of the socket 7 with a respective receiving seat in the work head, as it is common in the art. Figures 4 to 12 show the work step sequence for the production of a tool 1 according to the present invention, the sequence including first feeding, e. g. by casting, an abrasive solution or mixture 4 into one or more cavities IM of a mould M, e. g. made of aluminum, then arranging on the mould M a vibration damping element 5, such as a rubber plate having through openings or holes 5a, whereby at least one opening or hole 5a is located at each cavity IM of the mould M, where the abrasive solution or mixture 4 is provided.

A support base 3 (e. g. a Velcro layer) is laid on the rubber plate 5, of course opposite to the cavity/cavities IM, and the mould M is pressure closed, e. g. against a counter-mould element CM, typically by displacing the counter-mould CM by means of suitable linear actuators 8. Preferably, the mixture 4 is heated, e. g. by means of heating means HM provided in the counter-mould (Figures 8 and 9), such as electrical resistors or by circulating a hot fluid. Thus, a partial migration or expansion of a portion of the abrasive solution or mixture 4 is caused throughout the opening/s 5a to impregnate, preferably not entirely, the support base 3. The abrasive solution or mixture 4 is leaved or caused to harden or solidify, e. g. by means of the pressure applied by the mould M or by heating, the heating being for example kept a temperature between 140 °C and 150 °C for 15 minutes. Once the hardening is completed, the counter-mould is removed and the moulded tool or tools are removed from the mould M.

The abrasive solution or mixture 4 is preferably made of epoxy resin, inert fillers, abrasive materials/granules.

In the attachment portion 2a, instead of Velcro 3, any suitable layer or fabric impregnatable by the abrasive solution or mixture 4 can be used, such as a fabric, a grid, e. g. made of plastic, or the like. The vibration damping element 5 can instead be made of rubber, and preferably of a material selected from the group including styrene rubber, nitrile rubber, butadiene-vinylpyridine copolymers, (neoprene) chlorobutadiene polymers, monoolefin polymers and copolymers, isobutylene polymers, polyethylene elastomers, such as a polymer obtained by sulphochlorination of polyethylene (HYPALON), or butadiene-ethylene-propylene terpolymers (EPDM), fluoroolefin elastomers, such as TFE HFP VDF terpolymer, acrylic elastomers, ethyl acrylate and butyl acrylate polymers and copolymers, fluoroacrylate polymers, polysulfide rubbers, polyester rubbers, silicone rubbers and natural rubbers obtained by coagulation of the latex from plants.

If a mould M having a plurality of cavities IM is used, after the removing step from the mould, the moulded tools can advantageously undergone a die- cutting operation to severe the various tools from one another.

According to a preferred variant (see Figure 13), the production of an abrasive or cutting tool according to the present invention includes the following operation step:

- arranging a support base or first reinforcement or stiffening layer 3 made of an impregnatable material on a counter-mould CM;

- arranging a vibration damping element 5, in which at least one through opening 5a is formed, on the support base 3;

- closing the counter-mould CM against a mould element M, at least one cavity IM being delimited between the counter-mould CM and the mould M;

- supplying, e. g. pressure supplying, an abrasive solution or mixture 4 into the cavity IM, whereby causing the supplied abrasive solution or mixture 4 to partly cross the through opening/s 5a to impregnate, preferably non entirely, the support base or first reinforcement or stiffening layer 3;

- leaving the abrasive solution or mixture 4 to harden or causing it to harden; and

- removing the moulded object from the counter-mould (CM) and mould (M) group.

As an expert will easily appreciate, a connection sheet 6 and a socket 7 can be anchored to the attachment portion 2a even before the moulding step, in which case at the end of the moulding operation, a tool 1 provided with socket is obtained.

Figure 14 shows a presently preferred plant 10 for carrying out the method according to the present invention, which, comprises, in sequence:

- a feeding and (by gravity) loading unit 1 1 of an abrasive solution or mixture 4 into an underneath mould M;

- a laying unit 12 for locating a vibration damping element 5, e. g. including a rubber roll which is unwounded automatically or by the operator and laid onto the mould;

- a laying unit 13 for locating a support base or first reinforcement or stiffening layer 3, also being unwound from a roll;

- a moulding unit 14, e. g. a pressure-heating unit; and

- a removing unit 15 for removing the moulded tools from the mould M. Advantageously, the plant 10 comprises conveyor means 16 intended to successively transport the molds M to the various stations, as well as a downstream die-cutting unit 17 intended to separate the molded portions (blocks or block abrasive portion) in the respective cavities from the adjacent molded portions, and an end stacking unit 18.

As will be understood, according to the present invention it is provided to mould the abrasive solution or mixture 4 directly on the vibration damping element 5, which was previously impossible, and thus the attachment portion 2a made of a hardened abrasive mixture had to be glued to a rubber support.

Moreover, in an abrasive part according to the present invention, the support base, for example the Velcro, is not entirely impregnated with the abrasive solution or mixture 4 and thus the same is not totally rigid, whilst ensuring a stable support for the work portion, i. e. the blocks or block.

Accordingly, a tool according to the present invention has good flexibility, ensured by the vibration damping element and a good connection thanks to the support base.

The above-described tool, method and plant are susceptible to numerous modifications and variations within the protection scope as defined by the claims.