“ABRASIVE MODULE AND CORRESPONDING MODULAR BELT”

FIELD OF THE INVENTION

The present invention concerns an abrasive module and a corresponding belt provided with abrasive modules that can be installed in an apparatus for processing the surface of sheet-like elements. In particular, the belt allows to perform smoothing, lapping and surface finishing processes, advantageously but not exclusively without the belt needing to be cooled with a liquid.

BACKGROUND OF THE INVENTION

In the ceramic sector for the production of slabs, plates, tiles and in general sheet-like elements used to cover walls and floors, it is known that these sheet like elements have to undergo a series of mechanical surface processes, for example smoothing and lapping, in order to obtain the required surface properties.

The sheet-like elements, for example in the case of porcelain and technical stoneware, are typically made with a ceramic support body which is possibly covered with an engobe layer where a decoration can be impressed, which is then covered with a surface layer of glaze or crystalline.

The sheet-like element thus obtained must be smoothed or lapped to reduce roughness, surface ridges, or to improve flatness and create a surface with desired roughness and/or flatness.

Currently, these processes are performed with apparatuses or machinery provided with one or more smoothing heads equipped with consumable abrasive elements which, rotating at high speed, act on the surface, removing a layer of a certain thickness therefrom.

Other known but less common apparatuses comprise one or more in-line processing units, each of which is provided with a modular abrasive belt equipped with abrasive modules, which is made to rotate in contact with the sheet-like element to be treated.

Abrasive belt apparatuses, unlike those with satellite heads, can function dry, that is, without needing a cooling liquid or removal of material, with obvious advantages related to water consumption, treatment and management.

Each abrasive module is made of one piece, with a consumable abrasive material, and comprises a base from which a plurality of abrasive elements protrude which are configured, during use, to exert the abrasive action on the sheet-like element.

The abrasive modules are produced by molding and sintering and, for reasons of cost, they are initially made in larger modular sheets which are then cut into different sections in order to obtain the modules.

One of the main problems related to this type of production concerns the extraction of the modular sheet from the mold. In fact, even if it is compact, the modular sheet is difficult to manipulate without breaking it. In this sense, the thickness of the base, which represents the difference in height between the base of the abrasive heads and the free edge of the mold, must have a thickness such as to stiffen the overall structure and guarantee a damage-free demolding, as well as a precise cut that does not cause cracks.

However, too thick a base makes the abrasive elements too rigid during use and unable to follow, in a dynamic and sufficiently flexible manner, the surface conformation of the sheet-like elements, often leading to an inhomogeneous removal of material and an indiscriminate flattening which does not take into account the surface morphology of the element.

In this case, the surface irregularities would be completely flattened, bringing to light the underlying layers of material, irreversibly damaging the batch being processed.

Especially in the case of an abrasive belt apparatus, the abrasive elements must be able to withstand high shear stresses without breaking or separating from the base.

Another problem of such modules concerns the application to dry-cooled apparatuses in which the shape of the abrasive elements and the coverage percentage with respect to the total surface of the base is fundamental to guarantee a correct heat exchange and effective discharge of the material abraded. For this reason too, the interaction between the abrasive elements and the base constitutes a limit to its thickness and a problem that has not yet been resolved.

There is therefore a need to perfect an abrasive module and a corresponding modular belt that can overcome at least one of the disadvantages of the state of the art.

In particular, one purpose of the present invention is to provide an abrasive module which is particularly easy to produce and which, during use, guarantees to the abrasive elements sufficient flexibility and resistance to shear stresses. Another purpose is to produce said abrasive modules in such a way that they simultaneously guarantee an optimal heat exchange in the air and an effective discharge of the material removed.

Another purpose of the present invention is to provide an abrasive belt provided with such modules that is able to adapt to the surface of the sheet-like elements to be treated, avoiding excessive removal of material, thus improving efficiency.

The Applicant has devised, tested and embodied the present invention to overcome the shortcomings of the state of the art and to obtain these and other purposes and advantages. SUMMARY OF THE INVENTION

The present invention is set forth and characterized in the independent claims. The dependent claims describe other characteristics of the present invention or variants to the main inventive idea.

In accordance with the above purposes, an abrasive module, which overcomes the limits of the state of the art and eliminates the defects present therein, comprises a base membrane from which a plurality of abrasive heads project.

The base membrane comprises a gripping substrate configured as a structure with solids and voids able to increase the contact surface area in order to allow part of the abrasive composite material that the abrasive heads consist of to pass inside it and grip. The part of abrasive composite material remains essentially limited to a thickness of the gripping substrate, the gripping substrate consolidating the base membrane and the abrasive heads together in a monolithic manner.

According to another aspect, the gripping substrate has a base layer with a planar conformation and a plurality of gripping elements that project from the base layer at least in the direction of the abrasive heads. Furthermore, the gripping elements define an irregular alternation of solids and voids between them, inside which the composite material is incorporated, remaining confined to the thickness of the gripping substrate.

The thickness of the base membrane, which is substantially equal to the thickness of the gripping substrate, is much thinner than the one created in the state of the art, thanks to the presence of a gripping substrate with the characteristics described above which facilitates the mass production of the modules and gives, during use, a certain flexibility to the base membrane and therefore to the abrasive heads.

According to another aspect, the thickness of the base membrane is substantially equal to the thickness of the gripping substrate. According to another aspect, the gripping elements have a filiform microstructure in the shape of a hook or slot.

According to another aspect, the gripping substrate is in contact with the base of the abrasive heads, and the gripping elements are incorporated inside the abrasive heads limited to a base portion thereof. According to another aspect, the ratio between the thickness of the base membrane and an initial height of the abrasive heads is comprised between 0.01 and 0.5, preferably between 0.02 and 0.16.

According to another aspect, the abrasive module has a plurality of incisions which penetrate the base membrane in a direction inclined to the plane on which the gripping substrate lies. The incisions partly separate the abrasive heads from each other into rows, groups or even individually.

According to another aspect, the space occupied by the abrasive heads with respect to the surface of the base membrane from which they project varies between 20% and 80%, preferably between 30% and 70%, even more preferably between 40% and 60%.

According to another aspect, the space between one row of abrasive heads and the next, or the preceding one, defines a passage channel and the ratio between a width of the passage channel and an initial height of the abrasive heads is comprised between 0.08 and 1.1, preferably between 0.16 and 0.6. Some embodiments also concern a modular abrasive belt having an abrasive surface facing, during use, toward a sheet-like element to be treated and an opposite guide surface which cooperates, during use, with a plurality of pulleys.

The modular abrasive belt comprises a first reinforced support layer, and a second interface layer of elastic material on which a plurality of abrasive modules as above are associated in succession.

BRIEF DESCRIPTION OF THE DRAWINGS These and other aspects, characteristics and advantages of the present invention will become apparent from the following description of some embodiments, given as a non-restrictive example with reference to the attached drawings wherein:

- fig. 1 is a perspective view of an abrasive module in accordance with some embodiments described here;

- fig. 2 is a top view of fig. 1 ;

- fig. 3 is a section view along the line III-III of fig. 2;

- fig. 3a is an enlarged detail of fig. 3 in which the conformation of the gripping layer is visible;

- fig. 3b is one of the possible embodiments of the gripping substrate of fig. 3a;

- figs. 4-8 are variants of the abrasive module of the present invention;

- fig. 9 is a lateral view of a modular abrasive belt in accordance with some embodiments described here;

- fig. 10 is a section along the line X-X of fig. 9.

To facilitate comprehension, the same reference numbers have been used, where possible, to identify identical common elements in the drawings. It is understood that elements and characteristics of one embodiment can be conveniently combined or incorporated into other embodiments without further clarifications.

DESCRIPTION OF SOME EMBODIMENTS We will now refer in detail to the possible embodiments of the invention, of which one or more examples are shown in the attached drawings, by way of a non-limiting illustration. The phraseology and terminology used here is also for the purposes of providing non-limiting examples.

Some embodiments described with reference to figs. 1-8 concern an abrasive module 10 for a modular abrasive belt 100, figs. 9-10. The modular abrasive belt 100 can be installed in a processing unit of an apparatus for the surface processing of sheet-like elements T, for example in the apparatus described in document WO2018/083571A1. The abrasive module 10 comprises a base membrane 11 from which a plurality of abrasive elements or heads 12 project.

The base membrane 11 and the abrasive heads 12 are made, in a single body, with an abrasive composite material defined by a polymeric matrix with dispersed abrasive charges.

The composite material is hard and has self-regenerating characteristics (self- reviving), that is, during its use, the consumption of an outermost layer brings to light the abrasive charges of the lower layer.

With particular reference to fig. 3a, the abrasive module 10 comprises a gripping substrate 13 completely embedded in the base membrane 11. The base membrane 11 therefore comprises the gripping substrate 13 and the composite material incorporated therein.

The gripping substrate 13 is configured as a structure with solids and voids, able to increase the contact surface area in order to allow part of the abrasive composite material that the abrasive heads 12 consist of to pass inside it and grip, in order to consolidate the base membrane 11 and the abrasive heads 12 together in a monolithic manner.

The part of abrasive composite material described above remains essentially limited to a thickness S of the gripping substrate 13 which consolidates the base membrane 11 and the abrasive heads together in a monolithic manner.

With reference to the example embodiment of fig. 3 b, the gripping substrate 13 comprises a base layer 13a with a planar conformation and a plurality of gripping elements 13b that project from the base layer 13a at least in the direction of the abrasive heads 12.

The substrate 13 has a thickness S which is substantially defined by the thickness of the base layer 13a and by the average height of the gripping elements 13b, as visible in fig. 3a.

The gripping elements 13b define an irregular alternation of solids and voids between them that create meatuses and canaliculi inside which the composite material which remains confined to the thickness S is incorporated.

The base membrane 11 and the gripping substrate 13 have substantially the same thickness S. In particular, the quantity of composite material that the base membrane 11 consists of, and with which the gripping substrate 13 is soaked, is the minimum necessary to fill the voids present in the structure of the gripping substrate 13.

The thickness S of the base membrane 11 is defined by the reciprocal distance between an operating surface 11a thereof, which is the surface facing toward the abrasive elements 12, and an opposite interface surface 1 lb, see for example fig. 3a or fig. 3b.

In this way, during the manufacturing step it is possible to limit the composite material that defines the base membrane 11 and at the same time allow a rapid and effective demolding of the sheet of modules from the mold. Furthermore, the base membrane 11 thus defined guarantees a sufficient overall cohesion with the abrasive heads 12. The particularly reduced thickness of the base membrane 11 and the presence inside it of the gripping substrate 13 allows the abrasive heads 12 to act on the surface of the sheet-like element T in a substantially independent and flexible manner, in order to follow its surface development. The gripping elements 13b can have a filiform microstructure in the form of a hook or slot, please see the enlarged detail shown in fig. 3b, or, in general, a geometry configured to improve the surface friction with the abrasive material during the molding step and subsequently in order to guarantee a solid anchorage.

According to an advantageous embodiment, the gripping substrate 13 can consist of a layer of Velcro®, a porous layer, a honeycomb layer or any structure whatsoever that can increase the surface area of contact with the abrasive mixture in the molding step.

In some embodiments, the gripping substrate 13 is in contact with the base of the abrasive heads 12, and the gripping elements 13b can be incorporated inside the body of the abrasive heads 12, limited to the base portion (see fig. 3b), in such a way as to define a more compact structure and increase the resistance of the abrasive heads 12 to shear stresses, during use.

The abrasive heads 12 have an initial height H, measured starting from the operating surface 11a of the base membrane 11, which is the same for all the abrasive heads 12, fig. 3. The height H decreases during the use of the abrasive module 10, due to the contact with the sheet-like element T being processed.

The ratio between the thickness S of the base membrane 11, that is, of the gripping substrate 13, and the initial height H of the abrasive heads 12 can vary between about 0.01 and about 0.5, preferably between about 0.02 and about 0.16.

The base membrane 11 is therefore particularly thin compared to the height H of the abrasive heads 12, and the presence of the gripping substrate 13 makes the base membrane 11 flexible so that, during use, the abrasive heads 12 can adapt to the surface conformation of the sheet-like element T in a desired manner.

As shown by way of example in figs. 4-8, the abrasive module 10 can have a plurality of incisions 14 which penetrate the base membrane 11 in a direction inclined, for example orthogonal, to the plane on which the interface layer 13a lies, or to the operating surface 11a and to the interface surface l ib, in order to make the abrasive heads 12 more autonomous/independent during use.

The incisions 14 at least partly weaken the base membrane 11.

The incisions 14 can be disposed in series, alternating empty spaces with solid spaces. The incisions 14 can partly separate the abrasive heads 12 from each other into rows, groups or even individually.

The incisions 14 can have a rectangular, circular, elliptical shape, or other shape, and can completely pass through the thickness S of the base membrane 11 or sink for only a part thereof.

The abrasive module 10 can have a rectangular shape and the abrasive heads 12 can be disposed in parallel rows, orthogonal to the longer side. For example, the abrasive module 10 can have a preferential development along an axis X. In the embodiment of fig. 6, the module 10, on the other hand, has the shape of a parallelogram.

The space between one row of abrasive heads 12 and the next, or the preceding one, defines a passage channel 15 through which, during use, the abraded material and the material released by the abrasive heads 12 are conveyed toward the outside of the abrasive module 10. To better identify the passage channel 15, this is outlined with a dashed line in figs. 4-8, for illustrative purposes only.

The distance L between one row of abrasive heads 12 and the adjacent one, measured in a direction substantially parallel to the axis X, defines the width, or in general a measurement, of the passage channel 15 of the abraded material. The ratio between the width L of the passage channel 15 and the initial height H of the abrasive heads 12 is comprised between about 0.08 and about 1.1, preferably it is comprised between about 0.16 and 0.6. A large L/H ratio promotes the evacuation of the material of the so-called third body, that is, both the material removed from the sheet-like element T and also the one released by the abrasive heads 12.

The passage channel 15 has a transverse orientation with respect to the axis of development X of the abrasive module 10 so that, during use, the material removed and released can be conveyed toward the outside.

In the examples of figs. 4-5 and fig. 7 the passage channels 15 are substantially orthogonal to the axis of development X, while in the examples of fig. 6 and fig. 8 the passage channels 15 are inclined and directed away from the axis of development X so that the removed/released material is, during use, conveyed toward the outside of the module 10.

The abrasive heads 12 have a shape and a reciprocal distance that maximize the heat exchange with the ambient air and the resistance to shear stresses. The abrasive heads 12 can have a rectangular, parallelogram-shaped, circular, elliptical or other cross-section, see for example figs. 4-5.

The abrasive heads 12 of a same abrasive module 10 can be all the same or they can also be different from each other. Advantageously, providing the abrasive heads 12 of the same shape allows to obtain a more uniform abrading capacity on the sheet and a more uniform heat exchange with the air.

In the case of different abrasive heads 12, they can have the same cross-section shape, but have different sizes, see for example figs. 1-2.

According to possible embodiments, not shown, the abrasive heads 12 can have grooves or corrugations on the lateral surface, preferably directed orthogonal to the base membrane 11, which are configured to increase the heat exchange surface and promote the export of heat from the abrasive heads 12.

The coverage percentage of the space occupied by the abrasive heads 12 with respect to the useful surface of the base membrane 11 varies between about 20% and about 80%, preferably between about 30% and about 70%, even more preferably between about 40% and about 60%. In a preferred and example configuration, the coverage percentage is comprised between about 45% and about 55%.

The Applicant has experimented that a coverage percentage of approximately 50% allows to optimize the heat exchange in the air for the cooling of the abrasive heads 12, and at the same time to carry out the desired processing on the sheet-like elements T.

Some embodiments described here, with reference to figs. 9-10, concern a modular belt 100.

The belt 100 has a closed loop configuration. The belt 100 has on one side an abrasive surface 111 facing, during use, toward a sheet-like element T to be abraded, and on the opposite side a guide surface 112 which cooperates, during use, with a plurality of pulleys in a manner per se known.

The belt 100 comprises a first support layer 113 flexible enough to, during use, wrap itself around the pulleys, and a second interface layer 114 consisting of an elastic material, on the interface layer 114 there being attached in succession a plurality of the abrasive modules 10 as above.

The abrasive modules 10 can be attached by gluing on the interface layer 114 with their interface surface lib, that is, on the side opposite to that from which the abrasive heads 12 project.

The abrasive modules 10 are disposed aligned with their axis of development X parallel to the direction of sliding of the belt 100.

The interface layer 114 can have seatings inside which a respective abrasive module 10 can be disposed. In this case, the abrasive module 10 can be attached by interlocking as well as by gluing.

With particular reference to fig. 8, this shows a cross-section of the abrasive belt 100 shown during the processing of a sheet-like element T, in which the contact interaction between the abrasive heads 12, deliberately emphasized to explain the concept, and the irregular surface of the sheet-like element T is promoted by the characteristics of thickness and constitution of the base membrane 11.

It is clear that modifications and/or additions of parts may be made to the abrasive module and to the corresponding modular abrasive belt as described heretofore, without departing from the field and scope of the present invention as defined by the claims.

In the following claims, the sole purpose of the references in brackets is to facilitate reading and they must not be considered as restrictive factors with regard to the field of protection claimed in the specific claims.