DESCRIPTION

The present invention refers to a tool for the roughing and/or polishing of hard surfaces such as stone, marble or the like.

In particular, the tool subject-matter of the present invention is of the type usable in association with hand-operated machines, such as an angle grinder or the like, for manual treatment of surfaces by an operator.

In the state of the art there are some solutions proposing a flexible disc, to be fixed to the mandrel of a grinder. On the work surface of the disc the machining abrasive members are fixed.

Flexibility of the disc-like bearing is an essential requisite, as it allows a bending of the abrasive disc, under the operator's pressure, so as to best adapt to the surface and therefore obtain a result that be the best possible.

However, the known discs have a reduced flexibility in the sense indicated herein. This is basically due to the fact that the abrasive members placed on the work surface are made in the form of metal strips on which the abrasive is deposited via a galvanic- type deposition process. Such metal strips are then anchored onto the elastic bearing, at the work surface, to cover most of it.

The metal strips, though flexible, greatly stiffen the support itself, relevantly limiting its possibility of bending in use. In particular, bending is limited depending on the arrangement and orientation of the metal strips, moreover making tool behavior non- homogeneous. This constitutes an evident limit of the known art.

Moreover, the attempting to overcome this bending strength, the high angular velocity reached by the disc in use, the friction exerted by the same on the surface to be worked, are factors unavoidably concurring to cause breakage of the metal strips and detachment of the same or of portions thereof from the elastic bearing. It is easy to imagine how a metal fragment detached from the bearing in rotation is flung tangentially at a remarkable speed, constituting a grave danger for the operator and/or whom is stationing in close proximity of the machining site.

Moreover, the detachment of even only one portion of strip makes the tool practically unusable, since the broken strips create gaps which would damage the surface to be treated. In addition, at such gaps particularly high stresses would be created, tending to speed up the process of deterioration and therefore of breakage and detachment of other portions of strip.

Therefore, such tools anyhow have a particularly short effective life and need to be replaced very frequently, with an evident rise in costs.

Hence, object of the present invention is to solve the problems still left open by the known art, and this is attained by a tool as defined in claim 1.

Further features of the device of the invention at issue are defined in the corresponding dependent claims.

The present invention, by overcoming the problems of the known art, entails several evident advantages.

In particular, it provides a roughing and/or polishing tool whose level of flexibility is extremely high, in any direction, regardless of how the tool is stressed in use.

Moreover, the tool described herein entails no risk of detachment of abrasive members in use. In fact, the manufacturing and the anchoring modes thereof to the bearing is such as to guarantee very high performances and the maximum possible safety for the operator.

Therefore, such features result in a more precise and safer machining, and in a much higher output of the tool, also because they allow to use for a longer time the same tool, with no need to replace it often. These and other advantages, along with the features and the operation steps of the present invention, will be made evident in the following detailed description of preferred embodiments thereof, given by way of example and not for limitative purposes. Reference will be made to the figures of the annexed drawings, wherein:

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

- Figure 2 is a sectional view of a tool according to a first embodiment of the present invention;

Figure 2A is a view of a detail of Figure 2;

- Figure 3 is a sectional view of a tool according to a second embodiment of the present invention;

- Figure 3A is a view of a detail of Figure 3;

- Figure 4 is an illustrative view of the use mode of a tool according to the present invention;

Figures 5A, 5B and 5C are views of a tool according to a third embodiment of the present invention;

- Figures 6A, 6B and 6C are views of a tool according to a fourth embodiment of the present invention; and

- Figures 7A, 7B, 7C and 7D are views of a tool according to a fifth embodiment of the present invention.

Hereinafter, the present invention will be described in detail with reference to the above-mentioned figures.

Referring initially to figure 1 , it shows a surface machining tool 1.

The tool 1 is of the type usable with a rotary machine, e.g. a grinder, a drill and the like.

From a structural standpoint, the tool 1 comprises an elastic bearing 2 of rubber. Preferably, the rubber of which said elastic bearing 2 is made is of thermoplastic type, in particular thermoplastic polyurethane which allows to obtain the desired flexibility and elasticity of the bearing, combining it with the right mechanical strength. However, it should be understood that other materials may be used, in particular rubbers, thermoplastic and non-thermoplastic ones, provided they exhibit equivalent technical and physical features.

Such bearing 2 preferably has a discoidal shape and comprises means for fastening to a mandrel of the rotary machine. E.g., such means can comprise a metal flange 10, equipped with connections and/or holes suitable for said fastening function. It is not deemed necessary to delve into the details of such means, as it could be different depending on the type of machine for which the tool is intended.

The bearing 2 has a surface 3, which herein will be referred to as work surface 3. The work surface 3 is the tool portion which, during a machining, contacts the material to be polished.

Of course, to be able to perform the function which it controls, the tool should be provided with abrasive material, at its work surface 3.

The elasticity and flexibility of the material of which the bearing 2 is comprised of is advantageous for allowing optimum adaptation of the bearing itself to the surface to be polished during the machining.

According to the present invention the tool 1 comprises a plurality of rigid abrasive members 4, anchored to the elastic bearing 2.

Each of said abrasive members 4 has a projecting portion 5 which projects from the work surface 3.

Advantageously, the abrasive members 4 are of a substantially point-shaped type, meaning by this that the extension of their projecting portion is remarkably shorter than the extension of the entire work surface 3. For instance, each projecting portion 5 of each abrasive member 4 may have a surface of an extension comprised between 15 and 80 mm ² .

Therefore, overall they assume a discrete, spot-like distribution, in which the abrasive members 4 are separated from each other by at least one portion of elastic bearing.

This allows to obtain a particularly advantageous flexibility, with respect to any pressing or bending action to which the tool be subjected in use. In fact, the bearing can bend, elastically, about each single point represented by one of the abrasive members 4.

Therefore, preferably, each one of the projecting portions 5 of the abrasive members 4 is button-, dome- or disc-shaped.

Of course, it is understood that on a same tool there could also be concomitantly provided abrasive members 4 of various type whose projecting portions 5 have different shapes, even depending on their location on the bearing 2.

Moreover, the abrasive members 4 comprise means for anchoring to the elastic bearing 2.

Next Figures 2 and 3, are sectional views illustrating two embodiments of the present invention, in connection with the anchoring modes of the abrasive members 4 to the bearing 2.

Such anchoring means may be of different type, but anyhow such as to guarantee a firm anchoring to the bearing itself and, above all, a reduction of the stress and strains to which the members 4 themselves are subjected in machining.

This makes the tool according to the present invention particularly safe, as it actually eliminates the risk that abrasive portions, in this case the abrasive members 4, may accidentally detach in use. According to a first embodiment, the anchoring means comprises a body 6, integral to the projecting portion 5, having a substantially frustoconical or frustopyramidal shape.

The body may advantageously be housed in corresponding seats obtained directly on the elastic bearing 2. A production process for a tool of this kind may envisage a step of moulding the elastic bearing. Therefore, at the mould-preparing stage the abrasive members 4 may be prearranged in position; their frustopyramidal or frustoconical bodies will remain embedded in the bearing itself, as illustrated in Figure 3A.

Advantageously, the side walls of the body 6 may be knurled to improve the seal; in addition, side bosses may be provided which further hold the abrasive member 4 integral to the bearing 2.

Alternatively, the anchoring means may be made so as to comprise a rod 7, integral to the projecting portion 5, and apt to be inserted into a corresponding through hole obtained in the elastic bearing 2. A corresponding fastening element 8 is then provided, so that it may cooperate with the rod at the surface 9 opposite to the work surface 3.

E.g., the rod 7 may be a threaded rod, and the fastening element 8 a corresponding nut 10. This embodiment is illustrated in Figure 2A.

In both cases, evidently, even when the tool is subjected to high-degree bending, each individual abrasive member is subjected merely to a minimum stress, especially a shearing stress, and held firmly anchored to the elastic bearing 2.

As to the manufacturing of the abrasive members 4, they comprise abrasive material on the surface of the projecting portion 5. The abrasive material will be set on the members 4 according to modes depending on the type of material of which the members themselves are made, and on the technologies selected and/or available.

Typically, yet this should not be construed as limitative, the abrasive material used for treating hard surfaces (marble, stone, or the like) is diamond.

For instance, the abrasive members could be made of metal or metal alloy, with a subsequent depositing of diamond grain on the projecting portion. The depositing could be carried out with galvanic methods or by means of vacuum-brazing, or by sintering.

Alternatively, or even in conjunction, the abrasive members 4 may be entirely or at least partly made of resin (or mixture of resins). In this latter case the abrasive material, e.g. the diamond grain, might be directly mixed to the resin, to form at least the projecting portion.

The technique for manufacturing the abrasive members will be selected depending on the intended use of the tool. In fact, different manufacturings are suited for different machinings. Some are more suited to roughing jobs, others are more suited to polishing jobs.

To obtain best performances, advantageously the elastic bearing has a substantially discoidal shape and, at rest, a convexity facing the work surface.

The abrasive members 4 could therefore be arranged so as to define lines and a pattern taking into account the bearing rotation. E.g., curved lines, preferably spiral- shaped ones can be provided, wound about the center of rotation of the tool.

Advantageously, each of the abrasive members 4 may be mounted idle on a bearing element, so as to be able to freely rotate with respect to the elastic bearing 2. This advantageously produces a lengthening of the life of the abrasive members, since they, by revolving on themselves, best exploit all of their surface extension. Next Figures 5A, 5B and 5C are views of a tool according to a third embodiment of the present invention.

In particular, it being understood that all of what has been described hereto holds true, according to said embodiment, the tool provides a plurality of peripheral abrasive members 14, arranged along an external periphery of the bearing 2.

In particular, according to said embodiment, four peripheral abrasive members 14 are provided, arranged at the ends of two orthogonal diameters of the disc 2, therefore at 90° the one to the other.

The peripheral abrasive members 14 have the purpose of allowing a correct machining also of angle parts, as illustrated in Figure 5C.

For this purpose, each of the peripheral abrasive members 14 should necessarily be arranged so as to come as close as possible to the external peripheral edge of the bearing 2, or, even better, so as to project with respect to said periphery.

According to the embodiment illustrated, as visible in Figure 5B, each of the peripheral abrasive members 14 covers also a corresponding side portion of the bearing 2.

Thus, in rotation, the two internal faces of the angle can be machined at the same time.

However, to further improve machining precision it is preferable that the peripheral abrasive members 14 be present in a number greater than four along the periphery of the bearing disc 2, so as to limit or eliminate gaps during rotation, in contact with the surface to be machined.

To this end, as illustrated in Figures 6A, 6B and 6C, a fourth embodiment of the tool according to the present invention is provided. In particular, according to said fourth embodiment, the peripheral abrasive members 14 are arranged, along the periphery of the bearing 2, at a mutual distance shorter than their size.

Also according to said embodiment, the peripheral abrasive members 14 are preferably arranged so as to project with respect to said periphery and cover also a corresponding side portion of the bearing 2.

Next, Figures 7A, 7B and 7C refer to a fifth embodiment of a tool according to the present invention.

In this case, the tool comprises substantially disc-shaped peripheral abrasive members 14 .

Preferably, according to such embodiment, also the abrasive members 4 are discshaped and manufactured according to the same technique. In particular, all abrasive members are manufactured by inserting rivet-type devices into the bearing 2.

Advantageously, as illustrated in Figure 7D, each of said abrasive members, both peripheral 14 and internal 4 ones, is disc-shaped and can be mounted idle on a bearing member, so as to be able to freely rotate with respect to the elastic bearing 2. This advantageously produces a lengthening of the life of the abrasive members, since they, by revolving on themselves, best exploit all of their surface extension.

The present invention has been hereto described with reference to preferred embodiments thereof. It is understood that other embodiments might exist, all falling within the concept of the same invention, and all comprised within the protective scope of the claims hereinafter.