AND METHOD FOR MAKING AN OPERATIVE UNIT

DESCRIPTION

Field of application

The present invention regards an operative unit for a disc-shaped rotary tool and a method for making an operative unit for a disc-shaped rotary tool.

The operative unit and the method, object of the present invention, are inserted in the industrial field of mechanical machining of metals, of composite materials, of polymers, of wood or other materials and in the field of production of precision tools.

In particular, the present operative unit can be employed for making a disc-shaped cutter adapted for example for executing cutting machining, or a disc-shaped grindstone adapted for example for executing machining via abrasion of metallic and non-metallic materials.

State of the art

As is known, disc-shaped cutters are employed in numerous manufacturing sectors in order to mechanically machine, under cold conditions, pieces constituted by materials which can have physical and mechanical characteristics that are even quite different from each other, such as wood, metallic materials, polymer materials or composite materials.

For such purpose, disc-shaped cutters are available on the market that are made of different materials and possibly provided with suitable coatings in order to allow, as a function of the specific material that the cutters are intended to machine, an optimal finishing and a suitable machining speed as well as in order to allow a good duration of the cutter.

For the machining of metals, cutters made of so-called hard metals have seen considerable diffusion in recent decades. Such hard metals are carbide powders, including in particular tungsten carbide, bonded by a metallic matrix, usually cobalt.

Conventionally the disc-shaped cutters comprise a machining body with discoid shape provided with a central through hole, for the engagement of the cutter to the mandrel of a machine tool, and with an external perimeter edge, along which a plurality of teeth are obtained spaced from each other, which together define the cutting edge of the cutter.

In order to improve the efficiency and the duration of the disc-shaped cutters, as well as of the cutting tools provided with such cutters, it is known to spray the cutters themselves, and possibly the cutting surface of the material to be machined, with cutting fluids. The flow of cutting fluid, in addition to cooling the cutter and the cutting surface of the material, in fact facilitates the removal of the chips and thus the advancement of the tool in the material subjected to machining.

In particular, cutting tools are known comprising multiple supply ducts, each of which connected to a source of a cutting fluid and provided with a delivery nozzle adapted to deliver a flow of the cutting fluid on the faces of the cutter of the tool.

Nevertheless, the cutting fluid distributed on the faces of the cutter has a hard time reaching the cutting edge thereof and thus has a hard time effectively cooling the zones of the cutter and of the piece to be machined that are more subjected to heating.

In order to facilitate an improved distribution of the cutting fluid towards the cutting zone, disc-shaped cutters have been designed that are provided on the main faces thereof with a plurality of radial grooves, adapted to receive the cutting fluid at their interior and to guide it - due to the centrifugal force imparted thereon during the operation of the cutter - towards the cutting edge.

One example of a disc-shaped cutter of the latter known type is reported in the patent US 4,624,237. More in detail, the cutter comprises a machining body with discoid shape, in particular made of steel, whose external perimeter edge bears, fixed thereto, an abrasive paste comprising diamond powder.

The machining body is provided with two opposite faces, a plurality of elongated grooves being made on each of these. Such grooves are substantially extended in radial direction, in particular with a curved extension.

The cutter described in the patent US 4,624,237 would nevertheless be poorly adapted to being used for facilitating the cooling of the cutting edge of the cutter itself.

The radial grooves made on the faces of the machining body of the cutter in fact facilitate the distribution of the cutting fluid towards discrete portions of the cutting edge and would therefore be able to ensure the suitable cutting fluid cooling of each of the teeth of the cutting edge of the cutter only for a pre-established number and arrangement of the teeth of the cutting edge along the external perimeter edge of the machining body.

The patent JP H0760650 describes a further disc-shaped cutter of known type which comprises a metallic machining body with discoid shape and a plurality of teeth fixed along the external perimeter edge of the machining body itself.

In addition, the cutter comprises a layer of abrasive material granules, such as diamond granules, deposited on the lateral faces of the machining body by means of electro-plating. Such abrasive material layer develops a reduced friction coefficient, generating a low level of noise during the cutting operations executed by means of the disc-shaped cutter.

The latter solution of known type described in the patent JP H0760650 does not at all solve the problem of the high overheating of the cutter in particular at the cutting edge of the cutter itself.

Also known are disc-shaped cutters provided with multiple machining bodies packed on each other in order to firmly operate on the product to be machined.

The latter type of cutters of known type particularly suffer the problem of overheating, in particular at the cutting edge along the height of the pack of machining bodies.

Presentation of the invention

The problem underlying the present invention is therefore that of overcoming the drawbacks shown by the abovementioned solutions of known type, by providing an operative unit for a disc-shaped rotary tool which allows, during the operation thereof, to efficiently supply a cutting fluid to the entire extension of the machining zone.

A further object of the present invention is to provide an operative unit for a disc-shaped rotary tool provided with greater efficiency than that currently available on the market.

Another object of the present invention is to provide an operative unit for a disc-shaped rotary tool which is entirely efficient and reliable in operation.

A further object of the present invention is to provide an operative unit for a disc-shaped rotary tool which can be made in a simple and inexpensive manner.

Another object of the present invention is to provide an operative unit for a disc-shaped rotary tool that is provided with optimal mechanical characteristics.

A further object of the present invention is to provide a method for making an operative unit for a disc-shaped rotary tool which is simple and inexpensive to implement.

Brief description of the drawings

The technical characteristics of the invention, according to the aforesaid objects, can be clearly found in the contents of the below-reported claims and the advantages thereof will be more evident from the following detailed description, made with reference to the enclosed drawings which represent several merely exemplifying and non-limiting embodiments of the invention, in which:

- figure 1 shows a perspective view of the operative unit according to the present invention, in accordance with a first embodiment; - figure 2 shows a plan view of the operative unit illustrated in figure 1 ;

- figure 3 illustrates a sectional view of the operative unit illustrated in figure 2 according to the trace III-III of figure 2 itself;

- figure 4 shows a plan view of a succession of machining bodies of the operative unit illustrated in figures 1-3;

- figure 5 shows a sectional view of the succession of machining bodies illustrated in figure 4, according to the trace V-V of figure 4 itself;

- figure 6 shows a perspective view of the operative unit according to the present invention, in accordance with a second embodiment;

- figure 7 shows a plan view of a detail of the operative unit illustrated in figure 6, relative to one of the machining bodies;

- figure 8 shows an exploded view of the operative unit according to the present invention, in accordance with a third embodiment;

- figure 9 shows a plan view of one of the machining bodies of the operative unit illustrated in figure 8;

- figure 10 shows a side view of the operative unit illustrated in figure 8, now assembled;

- figure 11 shows a detail of figure 10 contained within the outline XI of figure 10 itself;

- figure 12 shows an exploded view of the operative unit according to the present invention, in accordance with a fourth embodiment;

- figure 13 shows a plan view of one of the machining bodies of the operative unit illustrated in figure 12;

- figure 14 shows a side view of the operative unit illustrated in figure 12, now assembled;

- figure 15 shows a detail of figure 14 contained within the outline XV of figure 14 itself.

Detailed description

With reference to the enclosed drawings, reference number 1 overall indicates an operative unit for a disc-shaped rotary tool, object of the present invention.

The present operative unit 1 is intended to be advantageously employed, in a per se known manner, in order to mechanically machine mainly mechanical pieces under cold conditions, and it was mainly designed for machining pieces made of metal; nevertheless, it can also be employed for machining pieces made of different materials, such as in particular made of composite or polymer materials or even of wood, without departing from the protective scope defined by the present patent. The operative unit 1 according to the present invention is in particular intended to be mounted on a rotation shaft of a rotary tool (such as a milling machine or a grindstone) in order to be driven in rotation.

The present operative unit comprises a succession of two or more machining bodies 2 of substantially discoid shape, in particular arranged packed on each other.

Each machining body 2 is provided with a rotation axis X, around which it is susceptible of rotating when the rotary tool - on which the operative unit 1 is mounted - is actuated.

In operation, the machining bodies 2, brought into rotation, are intended to be placed in contact with a piece to be machined, in particular in order to remove chip material from such piece (if the operative unit 1 is applied to a cutter), or via abrasion (if the operative unit 1 is applied to a grindstone).

Each machining body 2 is provided with a first face 3 and with a second face 4, preferably parallel to each other, facing opposite to each other and substantially orthogonal to the rotation axis X of the machining body 2 itself.

In addition, each machining body 2 is provided with an outer profile 5, which is extended around the rotation axis X of the machining body 2 itself and delimits, at its interior, the first face 3 and the second face 4 of the machining body 2.

The outer profile 5 of the machining bodies 2 defines the part of the operative unit 1 intended to come into contact with the machining surface of the piece to be machined.

In particular, the overall thickness of the outer profiles 5 of the machining bodies 2 in succession defines a work surface of the operative unit 1 intended to operate in contact on the piece to be machined.

Advantageously, each machining body 2 is provided with an inner profile 6 extending around the rotation axis X within the outer profile 5 of the machining body 2 itself, in particular in a manner such that the inner profile 6 and the outer profile 5 delimit the first face 3 and the second face 4 of the machining body 2 between them.

Preferably, the inner profile 6 of each machining body 2 delimits, at its interior, a through hole 7 in particular aligned with the rotation axis X of the machining body 2 itself.

Advantageously, each machining body 2 has a diameter comprised between about 15 mm and 200 mm, e.g. about 80 mm, and has a thickness comprised between 0.1 mm and 6 mm, e.g. about 2 mm.

Advantageously, in accordance with the embodiments illustrated in figures 1-5 and 12-15, relative to examples of operative units 1 for disc-shaped cutters, the machining body 2 is provided with a plurality of teeth 8 distributed along the outer profile 5 of the machining body 2 itself.

The teeth 8 are advantageously arranged equidistant from each other along the outer profile 5. Otherwise, the teeth 8 can have a different distribution along the outer profile 5, e.g. with variable pitch, without departing from the protective scope of the present patent.

In accordance with the embodiments illustrated in figures 6-7 and 8-11, relative for example to operative units 1 for grindstones, the outer profile 5 of each machining body 2 has circular shape in order to allow removing material via abrasion from the piece to be machined.

Preferably, in particular if the operative unit 1 is intended to be mounted on a disc-shaped cutter, each machining body 2 is made of sintered metal material, in particular made of hard metal such as tungsten carbide, or of a sintered ceramic material (comprising for example particles of silicon nitride, alumina, titanium powders, etc.).

Advantageously, in particular if the operative unit 1 is intended to be mounted on a grindstone, each machining body 2 is made with a binder material (such as a resinoid binder or a ceramic binder or a metallic binder) mixed with diamond powder.

The machining bodies 2 of the operative unit 1 are placed in succession, aligned with each other along their rotation axis X, with the second face 4 of each machining body 2 placed in abutment against the first face 3 of the subsequent machining body 2.

In particular, the machining bodies 2 in succession comprise a first machining body 2' of the succession and a last machining body 2" of the succession itself, where the first face 3 of the first machining body 2' and the second face 4 of the last machining body 2" are not in abutment against other machining bodies 2.

In accordance with the particular embodiments illustrated in the enclosed figures, the operative unit 1 comprises three machining bodies 2 packed in succession.

Of course, the orientation of the succession of machining bodies 2 employed in the present description does not involve any limitation of the spatial arrangement of the operative unit 1, in particular of tilt or of vertical or horizontal orientation. For example, the operative unit 1 can be arranged with the rotation axis X vertical or horizontal or with any other tilt, with the first machining body 2' which can be arranged in a lower, upper or lateral position.

Of course, the operative unit 1 can also comprise only two machining bodies 2 or more than three machining bodies 2, without departing from the protective scope of the present patent. Advantageously, in order to facilitate the cooling of the machining bodies 2 during the operation of the operative unit 1, i.e. during the machining of the piece, a cutting fluid is distributed to the machining bodies 2, in particular constituted by a coolant and possibly lubricant liquid, such as water, oil or suitable usually aqueous emulsions.

In accordance with a different operating option, the operative unit 1 can also function under dry conditions, i.e. without cutting fluid supply.

According to the present invention, the operative unit 1 is provided with multiple inner channels 9, which are delimited between the pairs of faces 3, 4 in abutment of the machining bodies 2 and are advantageously intended, during the operation of the operative unit 1, to be traversed by the cutting fluid in order to convey the latter at the outer profile 5 of the machining bodies 2.

More in detail, the aforesaid inner channels 9 are delimited between the second face 4 of each machining body 2 and the first face 3 of the subsequent second machining body 2 and come out in the outer profile 5 of the machining bodies 2 themselves.

In particular, the inner channels 9 of the operative unit 1 are distributed, along the rotation axis X, substantially over the entire height of the succession of machining bodies 2.

In this manner, such inner channels 9 are arranged for distributing the cutting fluid in a uniform manner over the entire height of the succession of machining bodies 2 at the outer profile 5 thereof.

Advantageously, the inner channels 9 are extended from the inner profile 6 to the outer profile 5 of the machining bodies 2, defining in particular, at the inner profile 6 of the machining bodies 2, inlet slits 10 through which the cutting fluid is susceptible of entering into the inner channels 9, and, at the outer profile 5 of the machining bodies 2, outlet slits 11 through which the cutting fluid is susceptible of exiting from the inner channels 9 in order to be distributed at the cutting edge of the operative unit 1.

The cutting fluid, delivered by the inner channels 9 at the outer profile 5 of the machining bodies 2, is capable of efficiently cooling the operative unit 1 along the entire machining zone that is more subjected to overheating phenomena.

Advantageously, at least one of the faces 3, 4 of each machining body 2 is provided with surface channels 12 which define, at least partially, the aforesaid inner channels 9.

In accordance with the particular embodiments illustrated in the enclosed figures 1-7, both the faces 3, 4 of each machining body 2 are provided with surface channels 12, in a manner such that, in particular, the surface channels 12 of the first face 3 of each machining body 2 define the inner channels 9 together with the surface channels 12 of the second face 4 of the subsequent machining body 2 placed in abutment against the aforesaid first face 3.

In accordance with a different non-illustrated embodiment, the surface channels 12 are made only at the first face 3 or at the second face 4 of the machining bodies 2.

In accordance with a further different non-illustrated embodiment, the first face 3 of the first machining body 2' and the second face 4 of the last machining body 2" lack surface channels 12, while the possible other machining bodies 2 interposed between the first and the last machining body 2', 2" are provided with surface channels 12 on both the faces 3, 4. Advantageously, the surface channels 12 of each machining body 2 communicate with each other, defining a network which is extended on the corresponding face 3, 4 of the machining body 2 itself.

In particular, the network defines a multiplicity of surface channels 12 which are intersected with each other in multiple intersection points on the corresponding face 3, 4 of the machining body 2, both radially and circumferentially with respect to the rotation axis X of the machining body 2 itself.

Preferably, the network of surface channels 12 is extended from the inner profile 6 to the outer profile 5 of the machining bodies 2, in a manner such to allow the passage of the cutting fluid from the through hole 7 to the cutting edge of the operative unit 1.

Advantageously, at least one of the faces 3, 4 of each machining body is provided with a plurality of island-shaped protrusions 13 which are separated from each other by the network of surface channels 12.

Preferably, in accordance with the embodiments illustrated in figures 1-7, both the faces 3, 4 of the machining bodies 2 are provided with the aforesaid protrusions 13.

In particular, figures 1-5 illustrate a first embodiment of the invention relative to an example of an operative unit 1 for disc-shaped cutters, while figures 6-7 illustrate a second embodiment of the present invention relative to an example of an operative unit 1 for grindstones.

Preferably, the protrusions 13 are integrally made with the machining body 2 and are made of the same material as the latter.

Advantageously, the protrusions 13 of the machining body 2 are radially and circumferentially distributed on the corresponding face 3, 4 of the machining body 2 itself and are separated from each other by the network of surface channels 12, which defines a bedplate from which the protrusions 13 are projected upward.

In particular, the protrusions 13 are circumferentially distributed around the through hole 7 of the machining body 2, and are radially distributed with respect to the rotation axis X of the machining body 2 itself.

More in detail, each protrusion 13 is laterally delimited by the sections of surface channels 12 which are intersected at such protrusion 13.

In particular, the protrusions 7 advantageously have maximum width much smaller than the radial extension of the machining body 2, in particular at least one order of magnitude smaller than the aforesaid radial extension.

The network of surface channels 12 is susceptible of guiding the cutting fluid released on the faces 3, 4 of the machining body 2 towards the outer profile 5 thereof.

In particular, the presence of the protrusions 13 distributed on the faces 3,4 of the machining bodies 2, i.e. the presence of the network of communicating surface channels 12, allows distributing the cutting fluid on the faces 3, 4 in a substantially capillary manner, hence allowing the cutting fluid - subjected to a centrifugal force imparted by the machining bodies 2 under rotation - to reach the entire outer profile 5 of the machining bodies 2 themselves in a substantially uniform manner.

In accordance with a preferred embodiment illustrated in the enclosed figures, the protrusions 13 are regularly spaced from each other.

Advantageously, each protrusion 13 has a height comprised between about 0.1 mm and 0.6 mm and preferably is about 0.3 mm.

The width of each surface channel 12, which separates the protrusions 13 from each other, is comprised between about 0.1 mm and 1.5 mm and preferably is about 0.4 mm.

In accordance with a particular embodiment not illustrated in the enclosed figures, each machining body 2 is provided with an annular support extending around the through hole 7 and defining the inner profile 6 of the machining body 2 itself. Advantageously the aforesaid annular support of the machining body 2 has a reduced thickness with respect to the thickness of the remaining part of the machining body 2 and is preferably provided with the aforesaid surface channels 12. In particular, the annular support is made of metallic material, such as aluminum, copper, bronze, steel etc.

Advantageously, the present operative unit 1 is susceptible of being mounted on a support body 14, for example made of metallic material, and adapted to bear, mounted thereon, the machining bodies 2 and to be fixed to the rotation shaft of the tool. Such support body 14 comprises a support shaft 15 rotatable around a longitudinal axis thereof and intended to be inserted within the through holes 7 of the machining bodies 2 aligned with the rotation axis X of the latter.

The rotary tool, with which the operative unit 1 is intended to be coupled, is provided with supply means adapted to supply the aforesaid cutting fluid intended to traverse the inner channels 9 defined between the machining bodies 2.

Advantageously, the supply means for the tool comprise a hydraulic circuit, which is supplied by a source of cutting fluid (e.g. obtained with a containment tank) and is provided with a hydraulic pump adapted to pump the cutting fluid with a specific pressure preferably comprised between 3 bar and 150 bar, e.g. between 70 bar and 100 bar.

With reference to figure 3, the support body 14 comprises at least one conveyance channel 16 provided with an inlet opening, intended to be placed in fluid communication with the supply means adapted to introduce the cutting fluid into such conveyance channel 16. In addition, the conveyance channel 16 is provided with at least one outlet opening in fluid communication with the inner channels 9, and in particular with the inlet slits 10 on the inner profile 6 of the machining bodies 2, in order to distribute the cutting fluid within the inner channels 9. In this manner, the inner channels 9, following the centripetal force induced by the rotation of the machining bodies 2, are susceptible of guiding the cutting fluid towards the outer profile 5 of the machining bodies 2 themselves and of making it exit from the outlet slits 11.

Advantageously, the support body 14 comprises a first abutment portion 17 and a second abutment portion 18 integral with the support shaft 15 and susceptible of retaining the succession of machining bodies 2 pressed against each other.

In particular, the first abutment portion 17 is susceptible of operating in abutment against the first face 3 of the first machining body 2', and the second abutment portion 18 is susceptible of operating in abutment against the second face 4 of the last machining body 2".

Preferably, the first abutment portion 17 of the support body 14 is extended projectingly from the outer surface of the support shaft 15, in particular extended around the support shaft 15 itself, in particular in flange form. Advantageously, the first abutment portion 17 is integrally made with the support shaft 15. Advantageously, the second abutment portion 18 of the support body 14 is provided with an internal opening in which the support shaft 15 is inserted and it is preferably fixed to the latter by means of screwing.

Advantageously, the support body 14 is provided with multiple conveyance channels 16 arranged around the longitudinal axis of the support shaft 15, preferably equidistant from each other.

Advantageously, each conveyance channel 16 is provided with a first section 16' which is extended between the inlet opening of the conveyance channel 16 itself (preferably made on the outer surface of the support shaft 15), and the first face 3 of the first machining body 2'. In addition, each conveyance channel 16 is provided with a second section 16" which extends from the first face 3 of the first machining body 2' to the second face 4 of the last machining body 2".

Advantageously, the first section 16' of each conveyance channel 16 is made in the thickness of a section of the support shaft 15 and preferably in the thickness of the first abutment portion 17. Preferably, the second section 16" of each conveyance channel 16 is made on the outer surface of the support shaft 15.

Advantageously, each conveyance channel 16 of the support body 14 (and in particular the second section 16" of such conveyance channel 16) is extended at least between the first face 3 of the first machining body 2" and the second face 4 of the last machining body 2" of the succession of the machining bodies 2, in a manner such to convey the cutting fluid into the inner channels 9 delimited between two adjacent machining bodies 2, and in particular in the surface channels 12 of the faces 3, 4 of all the machining bodies 2.

Advantageously, in accordance with the embodiments illustrated in figures 6-15, at least one face 3, 4 (and preferably each face 3, 4) of the machining bodies 2 comprises first lowered sectors 19, preferably substantially flat, and second sectors 20 alternated with the aforesaid first sectors 19 around the rotation axis X of the corresponding machining body 2 and extending in relief on the corresponding face 3, 4 with respect to said first (lowered) sectors 19.

In particular, each second sector 20 (in relief) of the face 3, 4 of the machining body 2 is inserted in the corresponding first (lowered) sector 19 of the subsequent machining body 2 adjacent to such face 3, 4.

More in detail, each second sector 20 of the second face 4 of each machining body 2 is inserted in the corresponding first sector 19 of the first face 3 of the subsequent machining body 2, and each first sector 19 of the second face 4 of the machining body 2 receives, at its interior, a corresponding second sector 20 of the first face 3 of the subsequent machining body 2.

Analogously, each second sector 20 of the first face 3 of each machining body 2 is inserted in the corresponding first sector 19 of the second face 4 of the preceding machining body 2, and each first sector 19 of the first face 3 of the machining body 2 has inserted, at its interior, a corresponding second sector 20 of the second face 4 of the preceding machining body 2. In particular, as illustrated for example in the embodiment of figures 6 and 7, each face 3, 4 of each machining body 2 is provided with the aforesaid first and second sectors 19, 20.

Otherwise, as illustrated for example in the embodiments of figures 8-16, the first face 3 of the first machining body 2' and the second face 4 of the last machining body 2" lack sectors 19, 20, while the possible other machining bodies 2 interposed between the first and the last machining body 2', 2" are provided with the sectors 19, 20 on both faces 3, 4.

Advantageously, the sectors 19, 20 are extended up to the outer profile 5 of the corresponding machining body 2.

Advantageously, the overall number of the sectors 19, 20 (first and second) of each face 3, 4 of the machining body 2 is greater than or equal to four, for example six (as in the example of figures 6 and 7) or sixteen (as in the example of figures 8-15).

In particular, each first sector 19 of each face 3, 4 is arranged between two second sectors 20 adjacent thereto of the same face 3, 4, and vice versa.

Advantageously, the configuration of the sectors 19, 20 on the faces 3, 4 of the machining bodies 2 ensures a high machining quality (via removal of chips or via abrasion) of the operative unit 1, in particular optimizing the machining precision at the line of separation between each machining body 2 and the next.

Along the aforesaid separation line, the work bodies 2 of the operative unit 1 tend to come into less contact with the surface of the piece to be machined.

The configuration of the sectors 19, 20 on the faces 3, 4 of the machining bodies 2 determines (as is visible in particular in the examples of figures 11 and 15) that the separation line between each machining body 2 and the next is extended around the rotation axis X with undulated progression.

In this manner, the work surface of the operative unit 1 has, along a circumferential line C (represented with a dashed line in figures 11 and 15), void sections (formed by the line of separation between two work bodies 2) alternated with solid sections (defined by the second sectors 20).

Consequently, in operation, when the operative unit 1 is rotated, at the lines of separation between the work bodies 2, the work surface of the operative unit 1 alternately operates with the void sections (in which it is less in contact with the piece to be machined) and with the solid sections which operate in full contact with the piece to be machined, removing possible machining imprecisions left by the preceding void sections. In this manner, an optimal machining quality is ensured even at the separation lines between the work bodies 2.

Advantageously, in accordance with the embodiment illustrated in figures 6 and 7 (relative to an operative unit 1 for grindstones), the second sectors 20 of the faces 3, 4 of the machining bodies 2 are provided with protrusions 13 which are extended in relief with respect to the first sectors 19 (preferably substantially flat).

The protrusions 13 of each second sector 20 of the second face 4 of each work body 2 are placed in abutment against the corresponding first sector 19 of the first face 3 of the subsequent machining body 2.

In this manner, in particular, the first sectors 19 define substantially lowered zones on the corresponding second face 4 of the machining body 2, in which the protrusions 13 are inserted that are made on the second sectors 20 of the first face 3 of the subsequent machining body 2 of the succession of machining bodies 2.

Advantageously, in accordance with the embodiment illustrated in figure 7, the protrusions 13 of the first face 3 of each machining body 2 (illustrated with solid line in figure 7) are offset with respect to the protrusions 13 of the second face 4 of the machining body 2 (illustrated with dashed line in figure 7) by a specific offset angle having vertex in the rotation axis X of the machining body 2. Preferably, the aforesaid offset angle has width substantially comprised between 1.5° and 3.5°.

Of course, the aforesaid offset position of the protrusions 13 is advantageously applied to the machining body 2 in accordance with any one of the above-described embodiments, in particular both in the embodiment of the machining body 2 provided with the aforesaid first and second sectors 19, 20 (as in the example of figure 7) and in the embodiments in which the protrusions 13 are substantially uniformly distributed on the faces 3, 4 of the machining body 2. Advantageously, with reference to the embodiments illustrated in figures 8-15, each second sector 20 of the machining body 2 delimits at least one interspace 30 with the corresponding first sector 19 (in which such second sector 20 is inserted) of the adjacent machining body 2. More in detail, each second sector 20 of the second face 4 of each machining body 2 delimits the corresponding interspace 30 with the corresponding first sector 19 (in which such second sector 20 is inserted) of the first face 3 of the subsequent machining body 2.

Preferably, each second sector 20 of the first face 3 of each machining body 2 delimits the corresponding interspace 30 with the corresponding first sector 19 (in which such second sector 20 is inserted) of the second face 4 of the preceding machining body 2.

The aforesaid interspaces 30 define, at least partially, corresponding inner channels 9 of the operative unit 1.

Preferably, each sector 19, 20 is extended in radial direction with respect to the rotation axis

X of the machining body 2, from the inner profile 6 to the outer profile 5 of the latter.

In particular, each interspace 30 (delimited between the corresponding sectors 19, 20) is extended from the inner profile 6 to the outer profile 5 of the machining bodies 2.

In particular, figures 7-11 refer to a third embodiment of the present invention relative to an operative unit 1 for grindstones, while figures 8-15 refer to a fourth embodiment of the present invention relative to an operative unit 1 for cutters (in which in particular the machining bodies 2 are provided with teeth 8).

Advantageously, each sector 19, 20 is extended widthwise, around the rotation axis X of the corresponding machining body 2 for a specific angle at the center a with vertex on the rotation axis X.

In particular, each second sector 20 is extended widthwise, around the rotation axis X of the corresponding machining body 2, between two flanks 20' (extending radially with respect to the rotation axis X) which delimit between them the corresponding angle at the center a of the second sector 20 itself.

Preferably, each first sector 19 of each face 3, 4 is delimited widthwise (around the rotation axis X) between two flanks 20' of two corresponding second sectors 20 (of the same face 3, 4) adjacent to such first sector 19.

In accordance with the embodiments illustrated in the enclosed figures, the sectors 19, 20 have substantially the same width. In accordance with different non-illustrated embodiments, the sectors 19, 20 can have widths different from each other. Advantageously, each second sector 20 of the second face 4 of the machining body 2 has width (between the two flanks 20') smaller than the width of the corresponding first sector 19 (in which such second sector 20 is inserted) of the first face 3 of the subsequent machining body 2.

In this manner, the aforesaid interspace 30 (and more in detail a lateral part 30' thereof) is delimited at least partially (within the corresponding first sector 19) between the second sector 20 of the second face 4 of the machining body 2 and the second sector 20 adjacent to the corresponding first sector 19 of the first face 3 of the subsequent machining body 2. In particular, the lateral part 30' of the interspace 30 is delimited between two flanks 20' facing each other of two corresponding second sectors 20 of two machining bodies 2 in succession.

More in detail, the lateral part 30' of the interspace 30 is delimited between the corresponding flank 20' of the second sector 20 of the second face 4 of the machining body 2 and the flank 20' facing thereto of the aforesaid second sector 20 adjacent to the corresponding first sector 19 of the first face 3 of the subsequent machining body 2.

In accordance with the embodiments illustrated in particular in figures 11 and 15, each interspace 30 is provided with two lateral parts 30', each arranged on the corresponding flank 20' of the second sector 20.

In accordance with a different non-illustrated embodiment, each interspace 30 is provided with only one lateral part 30' arranged at one of the flanks 20' of the second sector 20, while the other flank 20' of such second sector 20 is in abutment against the flank 20' facing thereto of the adjacent second sector 20 of the subsequent machining body 2.

In accordance with the embodiments illustrated in the enclosed figures 8-15, each second sector 20 of the first face 3 of the machining body 2 has width (between the two flanks 20') smaller than the width of the corresponding first sector 19 (in which such second sector 20 is inserted) of the second face 4 of the preceding machining body 2, in this case defining corresponding lateral parts 30' of the interspaces 30 in a manner analogous to that discussed above.

Advantageously, each second sector 20 is provided with a corresponding top face 20A, extending preferably in a continuous manner between the two flanks 20' of the second sector 20, in particular with flat form and preferably orthogonal to the rotation axis X of the machining body 2. More in detail, in accordance with the embodiments illustrated in figures 8-15, each second sector 20 is formed by a solid body (preferably integral with the corresponding machining body 2) which defines the corresponding top face 20A which is continuous and in relief on the face 3, 4 of the machining body 2.

In particular, the top face 20A is extended without interruption from one of the two flanks 20' to the other of the corresponding second sector 20 (and preferably from the inner profile 6 to the outer profile 5 of the machining body 2), preferably with flat form.

In accordance with a different non-illustrated embodiment, each second sector 20 is formed by multiple bodies spaced from each other (preferably made integrally with the corresponding machining body 2).

Advantageously, each first sector 19 defines a corresponding bottom face 19 A, preferably flat, arranged lowered with respect to the second sectors 20 of the same face 3, 4, and in particular orthogonal to the rotation axis X of the machining body 2.

Preferably, each second sector 20 is elevated like a step on the corresponding face 3, 4 of the machining body 2, in particular with the flanks 20' substantially orthogonal to the bottom faces 19A of the adjacent first sectors 19 of the same face 3, 4.

Advantageously, the height (along the rotation axis X) of each second sector 20 (in relief) is defined as the distance between the corresponding top face 20 A and the bottom faces 19A of the first sectors 19 of the same face 3, 4 adjacent thereto; the depth (along the rotation axis X) of each first (lowered) sector 19 is defined as the distance between the corresponding bottom face 19A and the top faces 20 A of the second sectors 20 adjacent thereto of the same face 3, 4.

Advantageously, each second sector 20 of the second face 4 of the machining body 2 has height smaller than the depth of the corresponding first sector 19 (in which such second sector 20 is inserted) of the first face 3 of the subsequent machining body 2.

In this manner, the interspace 30 (and in particular a central part 30" thereof) is delimited at least partially between the top face 20A of the second sector 20 of the second face 4 of the machining body 2 and the bottom face 19A of the corresponding first sector 19 of the first face 3 of the subsequent machining body 2.

Preferably, in accordance with the embodiments illustrated in figures 11 and 15, each second sector 20 of the first face 3 of each machining body 2 is in abutment against the corresponding first sector 19 (in which such second sector 20 is inserted) of the second face 4 of the preceding machining body 2, in particular with the top face 20A of such second sector 20 in abutment against the bottom face 19A of the corresponding first sector 19.

In accordance with alternative embodiments, not illustrated in the enclosed figures, each interspace 30 can be constituted by only the central part 30" (without the lateral parts 30') or by one or both lateral parts 30' (without the central part 30').

Preferably, each interspace has width (according to the rotation axis X) substantially constant and equal for example to about 0.05 millimeters.

Advantageously, the making of the inner channels 9 by means of the interspaces 30 allows the cutting fluid to exit along the separation lines (between subsequent machining bodies 2) with undulated progression (defined by the sectors 19, 20), therefore facilitating a uniform distribution of the cutting fluid along the height of the operative unit 1 according to the rotation axis X.

In accordance with an embodiment not illustrated in the enclosed figures, the interspaces 30 are obtained by means of grooves made on the top face 20A of the second sectors 20 and/or on the bottom face 19A of the first sectors 19.

Advantageously, the first sectors 19 of the first face 3 of the machining body 2 are offset with respect to the second sectors 20 of the second face 4 of the same machining body 2 by a specific shift angle σ having vertex in the rotation axis X and preferably smaller than the aforesaid angle at the center a of each sector 19, 20.

In accordance with the examples of figures 8-15, the aforesaid shift angle σ is equal to about half of the angle at the center a of each sector 19, 20.

In this manner, in particular, the projection on the plane (orthogonal to the rotation axis X) of the work body 2 of each first sector 19 of the first face 3 is partly superimposed on one of the first sectors 19 and on one of the second sectors 20 (adjacent to each other) of the second face 4.

Advantageously, with reference in particular to the embodiment of the present invention illustrated in figures 1-5, each machining body 2 comprises at least one or more centering bores 21, each placed off-center with respect to the rotation axis X (and in particular with respect to the through hole 7) of the machining body 2 and extending so as to pass between the first face 3 and the second face 4 of the machining body 2 itself.

Each centering bore 21 of each machining body 2 is aligned with the corresponding centering bores 21 of the other machining bodies 2 of the succession of machining bodies 2. The operative unit 1 comprises one or more centering pins 22, each inserted to size in the corresponding centering bores 21 (aligned with each other) of the machining bodies 2.

Advantageously, the centering pins 22 are intended to be interposed between the first abutment portion 17 and the second abutment portion 18 of the support body 14, in particular in a manner such to prevent the exit of the centering pins 22 from the corresponding centering bores 21 of the machining bodies 2.

The aforesaid centering pins 22, inserted in the corresponding aforesaid centering bores 21 of the machining bodies 2, allow preventing relative rotations of the machining bodies 2 around the support shaft 15, in particular in order to prevent shifts of the teeth 8 of each machining body 2 with respect to the other machining bodies 2 of the operative unit 1.

Of course, the centering bores 21 and the centering pins 22 can also be applied to other embodiments of the present invention, such as to the fourth embodiment illustrated in figures 12-15.

Also forming the object of the present invention is a method for making an operative unit 1 of the above-described type, and in particular of the type relative to the first embodiment illustrated in figures 1-5, the reference numbers thereof being maintained hereinbelow.

The present method comprises a step for making at least one centering bore 21 (and preferably multiple centering bores 21, e.g. at least two) in each machining body 2.

Each centering bore 21 is placed off-center with respect to the rotation axis X of the corresponding machining body 2 and is extended so as to pass between the first face 3 and the second face 4 of the machining body 2 itself.

Advantageously, such step for making the centering bores 21 is obtained during the molding of the machining body 2, in particular by means of a sintering process.

Otherwise, the step for making the centering bores 21 is obtained by means of milling machining or by means of a process of spark erosion (e.g. plunge milling). In particular, the milling machining is actuated after a pre-sintering process of the machining body 2 and before the sintering process applied to the machining body 2 itself. The spark erosion process is advantageously actuated after the sintering process.

Preferably, each centering bore 21 has diameter on the order of millimeters, and for example is about one millimeter.

In particular, the size of the centering bores 21 obtained with the aforesaid production step has a precision on the order of tenths of a millimeter. Advantageously, a stage is provided for grinding the faces 3, 4 of the machining body 2; in particular, such stage comprises a preliminary grinding by means of the use of a coarse-grain grindstone in order to reduce the thickness of the machining body 2 if necessary and a second fine grinding, by means of the use of a fine-grain grindstone, in order to finish the faces 3, 4 and reduce the surface roughness thereof.

The present method also comprises a step for coupling the machining bodies 2, in which the latter are placed packed on each other, aligned along the rotation axis X of the machining bodies 2 themselves.

In particular, the first face 3 of each machining body 2 is placed in abutment against the second face 4 of the subsequent machining body 2. The centering bores 21 of each machining body 2 are axially aligned with the corresponding centering bores 21 of the other machining bodies 2. Advantageously, the machining bodies 2 are positioned with the through holes 7 axially aligned with each other.

Subsequently, a step is provided for fixing the machining bodies 2, in which the latter are retained integral with each other to form a row of machining bodies 2 integral with each other, by means of suitable retention means such as a vice.

Then, the present method comprises a step for grinding the centering bores 21, preferably by means of spark erosion, in order to define, to size, a same width for the centering bores 21 themselves.

In particular, the size of the centering bores 21 obtained with the aforesaid grinding step has a precision on the order of hundredths of a millimeter.

A subsequent step is then provided for the insertion to size of the corresponding centering pins 22 within the centering bores 21 aligned with each other, in order to prevent any variation of relative position of the machining bodies 2 of the succession of machining bodies 2 themselves.

Subsequently, a step is advantageously provided for mounting the succession of machining bodies 2 on the support body 14.

In particular, such mounting step preferably provides for removing the retention means (e.g. the aforesaid vice) from the succession of machining bodies 2 and inserting the support shaft 15 of the support body 14 in the through holes 7 of the machining bodies 2 until the first face 3 of the first machining body 2' is brought into abutment against the first abutment portion 17 of the support body 14. Then, it is provided to fix the second abutment portion 18 of the support body 14 to the support shaft 15, e.g. by means of screwing according to that described above, until the second abutment portion 18 is brought against the second face 4 of the last machining body 2" of the succession of machining bodies 2, in order to retain the latter compressed between the two abutment portions 17, 18 of the support body 14.

The present method then provides for a step of machining the succession of machining bodies 2 integral with each other, with the centering pins 22 inserted in the corresponding centering bores 21 of the machining bodies 2 themselves.

In particular, if the operative unit 1 is intended to be applied to a cutter, the aforesaid machining step provides for executing a toothing process for the sintered machining bodies 2; by means of such process, the teeth 8 are obtained along the outer profile 5 of the machining bodies 2, in particular by means of the use of a diamond grindstone.

Preferably, the machining step provides for, after the toothing process, a profiling process by means of which the teeth 8 are shaped with the desired form. Such profiling process is for example obtained by means of the use of a diamond grindstone.

The invention thus conceived therefore attains the pre-established objects.