The present invention is devoted to the mechanical fixing tools for working with wood and similar tools and it generally refers to a fixing device for cutting mills.

More particularly, the invention relates to a device for fixing and locking the cutting inserts (also called cutting edges or knives) used for cutting mills, in particular for rotary-type cutting mills.

Specifically, the object of the present invention is a system for inserting and hooking a cutting tool into a receptacle, whose peculiarity is that of comprising means suitable for simplifying the exchange of the cutting tools and at the same time for responding to the needs of the production according to which machinery with high rotation speeds (up to 120 m/s) and minimum masses are employed; the system also guarantees high production performances, also minimizing the mechanical stresses of the structure and assuring a finishing of the maximum surface of machined elements in all working conditions (either along the wood wein and transversally with respect to the wood vein).

It is known that the cutting tool industry includes many applications depending on the type of mounting of the tool on respective supports. It is also known that particular cutters are used; said cutters usually consist of a cylindrical or pyramidal body on which a series of blades or cutting inserts or edges are arranged. Usually the cutting edges are mechanically fixed to the metal body of the cutter and they can be replaced after consumption and/or regenerated by regrinding.

Said cutting edges are fixed on the body of a cutting mill by means of various systems, the main purpose of which is to allow a suitable locking, as well as the simple replacement of the edges, in case of wear and tear or breakage or when it is necessary to turn said edges by using reversible knives.

Therefore, the cutting inserts or edges are normally inserted in suitable seats made on the body of the cutter or cutting mill and the relative locking is carried out through the use of anchors retained with screws arranged in a radial or tangential direction with respect to the cutting mill.

Moreover, according to the known technical solutions, the cutting insert is positioned inside a respective seat almost always with a reference on the base of said insert; the above feature causes the cutting insert to undergo radial displacements, due to the action of the centrifugal force which is opposed only by friction by the clamping force of one or more elements, which normally act through one or more screws and which, for this reason, are not enough to prevent the movement.

Nowadays, systems are also known which provide as reference a point supporting the cutting insert so as to block any possible displacement of said insert caused by the centrifugal force; in this case, elastic positioning elements are usually used for placing the cutting insert, and the above known systems differ from each other mainly due to the position of the elastic element and to its functionality.

In particular, the elastic element can be placed inside the receptacle, either directly in the cutter body, or in the fixing element where the clamping screw acts.

Alternatively, the elastic element can be placed in the cutter body, parallel to the insert or angularly arranged with respect to said insert within the available space, so as to produce a unidirectional (and therefore only radial) thrust or a bi-directional thrust (if the base of said insert has a sloping plane opposite to the cutting plane).

The above bi-directional thrust would therefore take place in a direction parallel to the insert, or in a radial direction (in the direction of the locking element), or in a direction opposite to the support plane of the insert which is formed by tightening the screws.

If the elastic element is placed inside the fixing element, a bi-directional thrust can be carried out only if the base of the insert is machined with a sloping plane which is parallel or divergent with respect to the upper plane corresponding to the cutting edge.

The object of the present invention is therefore to overcome the aforementioned drawbacks and, in particular, to provide a blocking device for cutting inserts or knives of cutting mills, which is provided with at least two or more seats for housing the cutting insert; said seats are made so as to guarantee a high tightness of the cutting insert, with a consequent precision of the cutting operation in all working conditions, in particular at high rotation speeds, without variations on the initial positioning of the cutting insert.

Another object of the present invention is to provide a blocking device for cutting inserts or knives of cutting mills, which has a reduced number of components with respect to the prior art, and which therefore has a considerable low construction complexity with respect to the known structures and techniques.

Another object of the present invention is to provide a blocking device for cutting inserts or knives of cutting mills, which has considerable flexibility in the use of different materials (steel-aluminum) of which the cutter body is made, as well as a considerable adaptability on the whole range of diameters and thicknesses of the cutter bodies and variability of the technological data (radial and axial cutting angles).

A further object of the present invention is to provide a blocking device for cutting inserts or knives of cutting mills, which allows a safe locking of the insert without stressing the cutter body.

These and other purposes, according to the present invention, are achieved by providing a blocking device for cutting inserts or knives of cutting mills, according to the attached claim 1.

Other detailed features are shown in the dependent claims.

Further characteristics and advantages of the blocking device for cutting inserts or knives of cutting mills, according to the invention, will become more clear from the following description, relative to a preferred but not limitative embodiment of the blocking device, and referred to the attached drawings, in which:

- figures 1 and 2 show two perspective views of a cutting mill’s body, in which a blocking device is made according to the invention;

- figure 3 shows a sectional and partially exploded view of the blocking device for cutting inserts or knives of cutting mills, according to the present invention; - figure 4 shows an enlarged sectional view of a cutting insert or knife used in the cutting mills of the previous figures, according to the present invention;

- figure 5 shows a perspective view of the cutting insert shown in figure 4;

- figure 6 shows a front view of the cutting insert shown in figure 4;

- figure 7 shows an enlarged view of the assembled blocking device of figure 3, according to the present invention.

With reference to the above mentioned figures, the blocking device according to the present invention is applied on a cutter body (1 ) of a cutting mill; the device is preferably made of steel or aluminum alloy and is preferably and susbstantially shaped as a cylinder, on which two or more seats (2) are made; the seats (2) where the cutting tools (knives) or cutting inserts (3) are housed are advantageously equally shaped.

Each seat or receptacle (2), together with the blocking elements of the device according to the invention, ensure maximum tightness and precision of each cutting insert (3) in all working conditions and, in particular, the seat (2) is able to withstand the high rotation speed of the cutter body (1 ) without causing variations ragrding the initial positioning of said cutting insert (3).

In particular, the blocking device which is the object of the present invention includes a cutting insert or knife (3), which rests on the cutter body (1 ) at a reference point consisting of a recess (4) of the insert (3); the recess (4) is coupled to an abutment (4') of the cutter body (1 ), where a correct radially working position is obtained and where the centrifugal force (13) is strongly opposed during the movement of the cutter body (1 ), so as to avoid radial displacements of the cutting insert (3) once said insert (3) is fixed; advantageously, a plug (8) is inserted in a suitable housing formed in the cutting insert (3), so that said plug (8) acts as a reference with respect to a required axial positioning and it is possible to work at high peripheral speeds, with a further increase in productivity and finishing.

The cutting insert (3) has an upper surface (3a) with an end lying on a first plane defined by two inclined axes (Y, X), which form an angle a <90°, and a lower surface (3b) with a lower end (3d) lying on a second plane defined by two inclined axes (U', X), which form an angle a'£a.

Furthermore, the recess (4) is interposed between the upper surface (3a) and the lower surface (3b) and has a length equal to the width (I) of the cutting insert (3).

Advantageously, the lower surface (3b) may have a first sloping surface section (3d) lying on the second plane defined by the axes (Y’, X) and a plane surface section (3e).

Still advantageously, the recess (4) is inserted into the abutment (4') and the abutment has a surface formed on each housing seat (2) of the cutter body (1 ); said abutment (4') preferably has also a length equal to or less than the width (I) of the insert (3) and a thickness equal to or less than the depth of the recess (4).

Moreover, in preferred embodiments of the invention, the cutting insert (3) has lowered sections (16), formed in the body of said cutting insert (3), at the recess (4), in which plastic material is inserted.

In each seat (2) of the cutter body (1 ), where the cutting insert (3) is fixed and locked, a blocking dowel (5) and at least one fixing screw (6) are also inserted, said dowel being coupled to a cutting-limiting device (10) and having an inner surface resting on the external surface of the cutting insert (3).

In particular, the cutting-limiting device (10) is configured to cut down the amount of material which has to be removed for a high safety of the operator, above all when operations with a manual dragging of the piece to cut out are performed.

Another function of the cutting-limiting device (10) is that of minimizing chipping due to the "chip breaker" effect, given that the end of the element is placed at a maximum value of 1 -2 mm below the cutting edge of the insert (3).

Advantageously, according to the present invention, at least one elastic element (7) is inserted in the blocking dowel (5) at a sloping plane (1 1 ) placed at the bottom of the cutting-limiting device (10) and at the first sloping surface section (3d) of the cutting insert (3), so as to push the insert (3) into a desired coupling position at the recess (4) of the insert (3) and at the abutment (4') of the cutting body (1 ).

For that purpose, the cutting insert (3) has a sloping plane (9) where the elastic element (7) inserted at the bottom of the dowel (5) on the sloping plane (11 ) is placed, thus allowing the elastic element (7) to gradually push the cutting insert (3) towards the abutment (4') during the screw (6) tightening phase.

The locking action of the screw (6), which, through the dowel (5), fits into a specific hole (15) made in the cutter body (1 ) at the seat (2), ensures a strong contrast against the centrifugal force (13) and guarantees a correct self-positioning of the insert (3) in the seat (2), both radially and axially.

This locking action also ensures a positioning stability of the insert (3) at high speeds of the mill (from 100 to 130 m/s), without any variation in the position of said insert (3). The result is obtained because a coupling is made between the insert (3) and the cutter body (1 ), which prevents any movement along the radial direction, i.e. along the direction of the centrifugal force (13).

Axial positioning is also guaranteed by a reference pin (8), which is placed in the insert (3) at the recess (4); said pin (8), in addition to the function of guaranteeing a reference with respect to the axial working position, counteracts the axial forces generated by the high rotation of the tool.

The blocking dowel (5) is made integral, both along the radial and the axial direction, with the cutting-limiting device (10) through a spring pin (14).

A further counteraction against the centrifugal force (13) is given by the plane (17) of the blocking dowel (5), which prevents a radial movement of said dowel (5).

Furthermore, the insert (3) may be sharpened on the surface (12) so that it can be reused; the reduction in the thickness of the insert (3) is recovered by the action of the elastic element (7), thus maintaining a correct tightening.

Therefore, it has been found that the solution object of the present invention allows to achieve the above mentioned objects and, in particular, allows to work at high peripheral speeds which are required by the new machinery, thus reaching an increase in productivity and finishing.

The seat (2) is configured to fix the cutting insert (3) on the cutter body (1 ), thus allowing the replacement of the insert (3), once used, with a new insert or with a sharpened insert, by maintaining a set positioning. Even if a sharpened insert is used and within a certain limit of sharpening, a positioning and a fixing of the tool configured to block the insert (3) in a safe and correct manner are also guaranteed, according to the present invention.

The removal, replacement and blocking operations of the cutting insert (3) take place according to the following steps:

- the tightening screws (6) are loosened so as to free the insert (3) from its seat (2);

- the insert (3) is taken from the receptacle or seat (2) and the seat is carefully cleaned;

- a new insert (3) is placed in the seat (2) along the same direction as the previous insert;

- the screw (6) is slowly tightened by keeping the insert (3) pressed with the base on the cutting-limiting device (10) towards the center of the cutter body (1 );

- a check is carried out to verify that the insert (3) is correctly coupled to the cutter body (1 ) also along the axial direction, with the reference pin (8) housed in its seat;

- the thrust on the insert (3) is loosened so that the elastic element (7) acts as a counteracting element, so as to push the insert (3), through the support surface (1 1 ), towards the radial reference position at the abutment (4');

- the screw (6) is firmly tightened by using a torque wrench according to given working instructions.

The features of the blocking device for fixing the cutting inserts of cutting mills, which is the object of the present invention, are clear from the above description, as well as the related advantages.

Finally, it is clear that many variations can be made to the blocking device of the invention, without departing from the novelty principles inherent in the inventive idea which is object of the appended claims, as it is clear that, in the practical embodiment of the invention, materials, shapes and dimensions of the details may be any according to requirements and said details may be replaced with other technically equivalent ones.