The present invention refers to a support for abrasive elements in sheet form for tools or machine tools . More in particular, the present invention refers to a support for abrasive elements in sheet form for honing tools or machine tools, wherein by honing we mean any mechanical removal operation of material from a surface made from wood, metal, masonry, glass, fiberglass, polymers, natural or artificial stone or other material, unprocessed or covered by a layer of coating.

In particular, by the term honing we mean to indicate any mechanical removal operation of material through the use of abrasives, irrespective of the type of abrasive used or of the degree of surface finishing obtained, like, purely as an example, sanding, grinding, roughing, honing or polishing operations .

Honing tools or machine tools are known that comprise a main body provided with a grip and with which a support of an abrasive element in sheet form is rotatably and removably associated.

The support consists of a body that has a rear surface for attaching to the main body of the tool or machine tool and a substantially flat front surface to which the abrasive element in sheet form is removably anchored.

The supports can be disc-shaped or polygonal, in particular rectangular, hexagonal or triangular; in industry jargon the first are indicated with the term "backing pads" and the second with the term "backing plates" .

The backing pads are commonly used in so called "random orbital sander" tools or machine tools, in which they are set in rotation both around their own axis and around one or more axes that are parallel and spaced apart with respect to the latter.

The backing plates, on the other hand, are used in so called "orbital" tools or machine tools.

The machine tools can be of the electric or pneumatic type. The abrasive element in sheet form, which in the industry jargon is indicated with the term "abrasive paper", in general comprises a base sheet that has a rear face intended to be coupled with the front surface of the support and the front face, intended to come into contact with the surface to be sanded, covered with abrasive material. The base sheet is flexible and consists of one or more layers of paper and/or other materials .

In known tools and machine tools, the anchoring of the abrasive element in sheet form to the support is obtained through a Velcro ^® coupling system made between the front surface of the support and the rear face of the base sheet or through an adhesive layer that covers the rear face of the base sheet .

During the honing operation it is necessary to take away the removed material in the form of dust that, otherwise, accumulates between the abrasive element in sheet form and the surface being worked on, obstructing and reducing the abrasive capability of the abrasive element and jeopardizing the quality of the work carried out on the surface. For this reason it has been known for a long time to take away the removed material through suction.

For such a purpose the support is crossed by a series of through holes that communicate with a manifold that is formed in the main body of the tool or ^' of the machine tool . The manifold is connected to a suction device or, alternatively, it is of the self-suction type itself thanks, for example, to a Venturi tube system through which dust is sucked and conveyed into a container.

Analogously, the abrasive element in sheet form is provided with a plurality of through holes .

The removed material is taken away by suction from the surface being worked on passing through the holes of the abrasive element in sheet form and of the support.

Typically, "backing pad" supports with a diameter of the order of 125-200 mm, or of whatever diameter, have from 6 to 20 holes, each with a diameter of the order of 10 mm and that are distributed equidistant from one another along one or more concentric circumferences. In "backing plate" supports, the holes are distributed along a perimeter strip of the backing plate and the average distance between two successive holes is at least of the order of 20-30 mm.

In order to ensure suction of the removed material it is necessary for the holes of the abrasive element in sheet form to have a configuration and sizes such as to be able to be on top of and aligned with the holes of the support or backing pad.

From what has been mentioned above it should be clear that each type of support or backing pad of the known type can be used exclusively with abrasive elements in sheet form equipped with a perforation corresponding exactly to that of the support or backing pad itself or in any case compatible with it .

Moreover, it is necessary for the abrasive element in sheet form to be mounted on the support or backing pad precisely so as to align the respective holes. If not, indeed, the suction of the removed material is jeopardized with consequent reduction of the quality of the work and of the abrasive capabilities of the abrasive element.

For this purpose it should be emphasized that the mounting of the abrasive element in sheet form on the support or backing pad of the tool or of the machine tool is manually carried out each time by a worker. Therefore, the accuracy of the mounting operation depends upon the skill and on the precision of the individual worker. Such an operation, moreover, since it indeed requires precision and accuracy, takes quite a long time to carry out with consequent idle time each time the abrasive element in sheet form is changed.

Moreover, an intermediate interface layer is often interposed between the abrasive element in sheet form and the front surface of the support, making it even more difficult to match the holes of one with those of the other.

The purpose of the present invention is that of making a support or backing pad for abrasive elements in sheet form for tools or machine tools that makes it possible to take away the removed material from the surface being worked on through suction, efficiently with any type of abrasive elements in sheet form.

Another purpose of the present invention is that of making a support or backing pad for abrasive elements in sheet form for tools or machine tools that makes it possible to simplify the mounting operations of the abrasive element in sheet form on it .

Another purpose of the present invention is that of making a support or backing pad for abrasive elements in sheet form for tools or machine tools that is particularly simple and functional, and that is cost-effective.

These purposes of the present invention are achieved by making a support or backing pad for abrasive elements in sheet form for tools or machine tools as outlined in claim 1.

Further characteristics are foreseen in the dependent claims .

The characteristics and the advantages of a support or backing pad for abrasive elements in sheet form for tools or machine tools according to the present invention shall become clearer from the following description, given as an example and not for limiting purposes, with reference to the attached schematic drawings, in which:

figure 1 is a schematic section view of a first embodiment of a support or "backing pad" according to the present invention;

figure 2 is a schematic section view of a second embodiment of the support or "backing pad" according to the present invention;

figures 3a-3d show plan views of some possible distributions of the suction openings of the support or "backing pad" according to the present invention.

With reference to the figures, a support or backing pad 1 for abrasive elements in sheet form for tools or machine tools, is shown.

More in particular, the present invention refers to a support for abrasive elements in sheet form for honing tools or machine tools, where by honing we mean any operation of mechanical removal of material from a surface .

In the attached figures, the abrasive elements in sheet form that can be applied to the support object of the invention and the tools or the machine tools to which the support object of the invention are applied and the relative suction devices are not shown, since they are known to the man skilled in the art and are not object of the present invention.

In particular, the honing tools or machine tools to which the support object of the present invention can be applied are of the rotary-orbital, multi-orbital, rectilinear type or producing all transmission movements, electric or pneumatic .

In the present description the terms "front" and "rear" or synonyms thereof should not be taken to limit the present invention. The term "front" or synonyms thereof refer to the exposure, when in use of the tool or of the machine tool, towards the surface to be worked. The term "rear" or its synonyms refers to the exposure, when in use of the tool or of the machine tool, towards the main body of such a tool or machine tool . The support or backing pad 1 comprises a first disc-shaped body 2, which has a rear surface 3 for attachment to a tool or machine tool and a front surface to which a second disc- shaped body 4 is fixedly associated.

The first disc-shaped body 2 is crossed in its thickness by at least one port 5 intended, when in use, to be connected to a suction device.

The second disc-shaped body 4 has a front surface 6 substantially flat on which to rest an abrasive element in sheet form and is crossed in its thickness by a plurality of suction openings 7 that communicate with the ports 5. A peculiarity of the present invention consists in the fact that the suction openings 7 are densely distributed substantially over the entire area of the front surface 6 or over at least one portion of it.

A further peculiarity of the present invention consists in the fact that the face of the front surface 6 that, when in use, faces towards the abrasive element in sheet form has a channelling 8 at the portions without the suction openings 7.

The channelling 8 is open towards the outside of the second disc-shaped body 4 and is in communication with the suction openings 7 themselves .

The expression "substantially over the entire area of the front surface or over at least one portion of it" means that the suction openings 7 are densely distributed over the entire area of the front surface 6 or over a portion of it except for, at most, some areas, such as for example its outer edge . By "densely distributed" of the suction openings 7 we mean to indicate a distribution such as that the suction openings 7 cover an area equal to at least 20%, preferably equal to 30%, of the area of the front surface 6 of the second disc-shaped body 4.

In such a case, there are at least one hundred suction openings 7 for a diameter of the second disc-shaped body 4 of the order of 150 mm and the active surface of which, i.e. the surface with the suction openings 7, is defined by an outer diameter of the order of 125 mm, outside of which there is an annular crown with a width equal to 12.5 mm not perforated, therefore, not active, and from which it is necessary to subtract the central hole of the order of 20 mm. Preferably, the number of suction openings is of at least 160 for such an active surface. In particular, the number of suction openings 7 is such that their number per unit surface is greater than or equal to 1, 2 openings per cm ² .

The suction openings 7, moreover, in the case in which they consist of through holes, as shall be made clearer in the rest of the description, have an average diameter of between 3 mm and 8 mm and, in a preferred embodiment, of between 2 mm and 6 mm, excluding the possible central opening with a greater diameter.

The suction openings 7, moreover, are distributed so that the distance between the perimeter of two suction openings 7 adjacent to one another is less than or equal to 5 mm and, in a preferred embodiment, such a distance is of the order of 3.7-3.8 mm. The suction openings 7, moreover, can all have the same diameter or can have a different diameter from one another .

As indicated above, the first disc-shaped body 2 has a plurality of ports 5, each of which consists of a through hole 50 or of a channel 51 open at the rear surface 3 of the first disc-shaped body 2, to communicate with the suction device, and at the front surface of the first disc-shaped body 2, to communicate with at least one suction opening 7 of the second disc-shaped body 4.

In the embodiment represented in the attached figures, the first disc-shaped body 2 comprises two disc-shaped elements 20 and 21 that are one on top of the other and fixedly coupled with one another.

One of these, the disc-shaped element 20, is intended to be coupled with the second disc-shaped body 4 and the other, the disc-shaped element 21, defines the rear surface 3 and is intended to be coupled with the tool or machine tool and in particular with the suction device.

In the disc-shaped element 20 the channels 51 and a first series of through holes 50' are formed.

In the disc-shaped element 21, on the other hand, a second series of through holes 50'' is formed, each of which is at a channel 51 or at a hole of the first series of through holes 50' of the other disc-shaped element 20 with which it defines a corresponding through hole 50.

The suction openings 7, in turn, comprise through holes 70 formed in the thickness of the second disc-shaped body 4 and each of them is in communication with at least one port 5 of the first disc-shaped body 2, whether it consists of a channel 51 or of a through hole 50.

In an alternative embodiment not shown, the suction openings 7 comprise slots or through slits in communication with at least one port 5 of the first disc-shaped body 2.

The suction openings 7 can thus consist of through holes 70 or of slots or through slits and, as an example, can have a cross-section that is circular, polygonal, oval or sickle-shaped.

It should be noted that the through holes can have orthogonal or oblique axis with respect to the front surface 6.

Advantageously, at least 50% of the suction openings 7 consist of through holes distributed over the front surface 6 except for the perimeter edge at which there are recesses.

In a preferred embodiment, one of the suction openings 7 is defined at the center of the second disc-shaped body 4 and has a greater diameter than the others. If present, such a central suction opening having a greater diameter acts as a centering element .

For this purpose it should be specified that by "centering" we mean a ^λλ rough" centering and not precise; according to the present finding, indeed, the abrasive element in sheet form does not require to be applied to the front surface 6 so as to make its holes exactly match and coincide with those of the support, operation that, on the other hand, requires a long time and precision.

The distribution of the suction openings 7 on the front surface 6 can be uniform or not and can follow different schemes . Figures 3a-3d show some possible distributions of the suction openings 7.

In figure 3a the suction openings 7 are distributed along concentric circumferences with respect to the center of the front surface 6, the suction openings 7 of two successive circumferences can be aligned with ^■ one another along the same radius or can be offset.

In figures 3b and 3c, the suction openings 7 are distributed along at least one series of first straight lines that are parallel to one another and along at least one series of second straight lines parallel to one another and intersecting the first.

In figure 3d, the suction openings 7 are distributed radially with substantially V-shaped radii that are offset with respect to one another; alternatively the radii can be rectilinear and/or curvilinear.

The channelling 8 is such as to ensure, when in use, a continuous suction air flow between the front surface 6 and the abrasive element in sheet form applied onto it in a direction parallel to the front surface 6 itself.

In one embodiment, the channelling 8 consists of a layer of velour or Velcro ^® , or alternatively of a layer that is technically equivalent and equipped with mushroom-shaped surface projections or similar, associated with the portions of the face of the front surface 6 that, when in use, faces towards the abrasive element in sheet form and without the suction openings 7.

For this purpose, it should be specified that the presence of the layer of velour or Velcro ^® , or other layer technically equivalent to it, like for example a layer equipped with mushroom-shaped surface projections or similar, on the front surface 6 of the support 1 as indicated above, is mainly intended to make the channelling 8.

It should be made clear, moreover, that by Velcro ^® or velour we mean a layer of material having a plurality of hook-and-loops .

In an alternative embodiment, the channelling 8 consists of a plurality of surface discontinuities formed on the portions of the face of the front surface 6 that, when in use, faces towards the abrasive element in sheet form without the suction openings 7.

In one possible embodiment, not represented in the attached figures, the discontinuities consist of a network of incisions and grooves.

In such a case, the abrasive element in sheet form shall be equipped, on its rear face, with an adhesive layer, however, the incisions or the grooves ensure the passage of air and dust .

In a further possible embodiment, not represented in the attached figures, the discontinuities consist of a plurality of ridges, bumps or surface irregularities.

The support or backing pad 1 is also provided with means 10 for attaching to the main body of a tool or machine tool of the type for example with threaded members.

The embodiments represented in figures 1 and 2 show different possible attachment means 10 of the threaded type. In figure 1 they consist of a threaded tang 11 fixedly attached to the first disc-shaped body 2 and in particular to its disc-shaped element 21. In figure 2 the attachment means 10 consist of a screw 12 that can be inserted into a central hole 13 that crosses - the support or the backing pad 1.

The support or backing pad 1 can be made, as an example, in rubber, polyurethane, sponge or other material associated with a stiffening element made from plastic, fiberglass, aluminum or similar, and can consist of a single piece or of many elements fixedly connected to one another according to the technology and manufacture requirements .

As already indicated, the support or backing pad 1 can be associated with an abrasive element in sheet form of any type.

In particular, the abrasive element in sheet form can have any type of perforation not necessarily corresponding to or compatible with the suction openings 7 of the support 1. Indeed, thanks to the fact that the suction openings 7 are densely distributed substantially over the entire area of the front surface 6 or over a part of it, the removal of the dusts from the surface being worked on by suction through the holes of the abrasive element in sheet form is in any case ensured, irrespective of the type of perforation of the abrasive element in sheet form and no matter how it is applied to the front surface 6 of the support or the backing pad 1. In particular, the suction is ensured even if the holes of the abrasive element in sheet form are not aligned with the suction openings 7.

The presence of the channelling 8, in any case ensures the suction of the dusts creating an air circulation gap between the rear face of the abrasive element in sheet form and the front surface 6 of the support or backing pad 1.

In light of the present description and of the attached figures, the man skilled in the art should not have any difficulty in identifying how the present invention operates .

The support or backing pad for abrasive elements in sheet form for tools or machine tools object of the present invention has the advantage of being able to be used with any type of abrasive element in sheet form, whatever it is, in particular, the perforation of such an element.

The support or backing pad object of the present invention, indeed, thanks to the fact that the suction openings defined on it are densely distributed substantially over the entire area of its front surface Or ₁ over part of it, ensures an effective suction of the dusts from the surface being worked on whatever the perforation of the abrasive element in sheet form applied to it.

The suction of the dusts of the material abraded from the surface being worked on is in any case ensured, on the portions of the front surface of the support or backing pad without the suction openings, due to the presence of a channelling that creates, between the support or backing pad and the abrasive element in sheet form, an air circulation gap .

The support or backing pad object of the invention, also has the advantage of simplifying the operations of mounting the abrasive element in sheet form on it, with or without the interposition of an interface layer. Indeed, it is not necessary to make the suction openings of one match the holes of the other, since the suction is ensured in any case .

Of course, if there is a central suction opening with a diameter that is greater with respect to the other ones, it facilitates the centering of the abrasive element in sheet form.

The support or backing pad object of the invention, thanks to the densely distributed suction openings on its front surface, also has the advantage of increasing the suction flow rate with respect to known supports.

The support or backing pad for abrasive elements in sheet form for tools or machine tools thus conceived can in any case undergo numerous modifications and variants, all covered by the invention; moreover, all the details can be replaced with technically equivalent ones . In practice the materials used, as well as the dimensions, may be any according to the technical requirements .