Patent Description:
The present invention relates to a method for balancing disc blades and to a machine implementing such a method.

More in detail, the present invention relates to a method and to a machine for balancing tipped disc blades. Use to which the description below will make explicit reference without however losing in generality.

As it is known, tipped disc blades consist of a flat central disc made of steel, which has a plurality of protruding radial teeth that jut out cantilevered from the perimeter edge of the disc equally angularly spaced to one another, and of a series of high-resistance material inserts or tips that are welded each on the crest of a respective radial tooth so as to form the cutting part of the same tooth.

To avoid undesired vibrations during cutting, at the end of the production process, the best disc blades are subjected to balancing so as to bring the center of mass of the disc blade at its symmetry and rotation axis.

The balancing of disc blades is currently carried out manually by an operator and entails manually removing, through grinding, a thin layer of metal material from the back of some of the teeth of the disc blade, so as to remove the excess material causing the unbalance.

More in detail, the disc blade balancing process requires operators to place the disc blade on a machinery capable of measuring the unbalance of the disc blade after having driven the blade into rotation about its symmetry and rotation axis. Once the disc blade has been analysed, the disc-blade balancing process requires the operator to remove the disc blade from the aforesaid machinery and, then, to use a grinding disc to manually remove a thin layer of material from the back of some given teeth based on their own experience and on the data displayed by the aforesaid machinery.

Finally, the disc-blade balancing process requires the operator to place the disc blade again on the machinery capable of measuring the unbalance of the disc blade, so as to check whether the selective material removal has brought the center of mass of the disc blade at its symmetry and rotation axis.

Clearly the balancing process described above can be repeated several times until the correct balancing of the disc blade is reached, namely until the unbalance measured by means of the machinery complies with a predetermined tolerance threshold.

Unfortunately, the balancing process described above requires a lot of time and the availability of skilled operators, with very high costs that this entails.

Furthermore, the balancing process described above is strongly affected by human errors. As a matter of fact, it often happens that, while grinding the teeth, the operator accidentally remove from the back of the teeth a layer of material thicker that requested, thus jeopardizing the mechanical resistance of the tooth of the disc blade, with the problems that this entails.

A disc blade with weak teeth cannot be sold and, hence, has to be rejected.

German patent application <CIT> discloses a method for balancing cup-shaped grinding disks for angle grinders that comprises the steps of measuring the unbalancing of the grinding disk and then the step of balancing such grinding disk by a material removal process, for instance by enlarging through holes already provided in the grinding disk.

<CIT> discloses cutter disks provided with through holes that allow to see through the spinning disks during cutting operation. In addition, <CIT> specifies that cutter disks may be dynamically balanced by removing material from holes edges.

Chinese utility model <CIT> disclose a circular saw blade comprising a central disk, a central through hole coaxial to the rotation axis of the blade, a plurality of balancing holes formed on the central disk, and a plurality of radially protruding teeth located extending cantilevered from the outer periphery of the outer perimeter edge of the central disk.

Chinese utility model <CIT> discloses a machine for balancing cylindrical rotors that comprises a spindle adapted to hold the rotor to be balanced in a vertical position and a drilling assembly adapted to perform balancing holes on the outer peripheral edge of the rotor, in a radial direction.

Lastly, Chinese utility model <CIT> disclose a machine for balancing cylindrical rotors that comprises a clamping vice provided with two opposite lateral jaws adapted to hold the rotor to be balanced and a drilling assembly adapted to perform balancing holes on the rotor.

Aim of the present invention is therefore to provide a method and a machine that are capable of speeding up the balancing of the disc blades described above and of making it more economic and precise, overcoming the drawbacks discussed above.

In accordance with these aims, according to the present invention there is provided a method for balancing disc blades as defined in Claim <NUM> and preferably, though not necessarily, in any one of the claims depending on it.

In addition, according to the present invention there is provided a machine for balancing disc blades as defined in Claim <NUM> and preferably, though not necessarily, in any one of the claims depending on it.

With reference to <FIG>, <FIG> and <FIG>, number <NUM> denotes, as a whole, a disc-blade balancing machine adapted to automatically balance a disc blade <NUM> preferably, though not necessarily, of the tipped teeth type.

More in detail, the machine <NUM> is adapted to make, in the disc blade <NUM>, one or more transversal holes with predetermined dimensions, in an eccentric position relative to the central or main axis of the blade, i.e. in an eccentric position relative to the symmetry and rotation axis A of the blade.

The term "disc blade" indicates, in particular, a rotary circular tool adapted to cut panels preferably large -sized, which are made of wood, plastic and/or similar materials, and are not necessarily flat. In other words, the term "disc blade" identifies a rotary circular tool which is adapted to make straight cuts in said panels and is preferably suited to be installed in cutting machines, such as for example table saws, miter saws and/or the like.

As shown in <FIG>, in particular, the disc blade <NUM> comprises: a central disc <NUM> preferably made of metal material, which extends coaxially to said symmetry and rotation axis A and is preferably provided with a central through hole <NUM> with a predetermined diameter; a series of protruding teeth <NUM> that jut out cantilevered from the perimeter edge <NUM> of central disc <NUM> in a substantially radial direction, and are spaced apart along the perimeter edge <NUM> preferably in a substantially regular manner; and, preferably, a series of tips or inserts <NUM> of high-resistance material, each of which is welded or brazed on the crest of a respective tooth <NUM> so as to form the cutting part of the same tooth <NUM>.

More in detail, the central disc <NUM> is substantially flat, and the radial teeth <NUM> are preferably made in one piece with the central disc <NUM>, and jut out cantilevered from the perimeter edge <NUM> of central disc <NUM> while remaining substantially coplanar to the midplane M of the disc, which, in turn, is substantially perpendicular to axis A. The radial teeth <NUM> define, together with the inserts <NUM>, the toothed crown of disc blade <NUM>.

The high-resistance material inserts <NUM>, in turn, are preferably made of a high-resistance metal material and are fixed on the respective protruding teeth <NUM> preferably by welding or brazing, so as to be arranged astride the tooth midplane that, in turn, can coincide or not with the midplane M of central disc <NUM>. Clearly, the inserts <NUM> can also be made of ceramic material, of a hybrid sintered material or the like, depending on the type of material they are going to cut.

In addition, the inserts <NUM> are preferably prismatic in shape with a substantially trapezoid or rectangular cross-section, and moreover they preferably have a minimum width measured perpendicularly to the midplane M, which is greater than the thickness δ of central disc <NUM>, so that the lateral sides of each insert <NUM> protrude cantilevered from opposite sides of the central disc <NUM> and of the tooth <NUM>.

In other words, the width of inserts <NUM> is such that, during cutting operations, only the inserts <NUM> come into contact with the piece/panel to be processed. On the contrary, the central disc <NUM> should never come into contact with the piece/panel to be processed during cutting operations.

The central hole <NUM> of the central disc <NUM>, on the other hand, is coaxial to the symmetry and rotation axis A of the blade.

With reference to <FIG>, moreover the central disc <NUM> is preferably provided with a plurality of preferably pass-through, peripheral openings or slits <NUM> which extend in a substantially radial direction insides the central disc <NUM>, starting from the perimeter edge <NUM>, and are specifically structured to allow/support local deformations of the blade toothed crown caused by temperature gradients generated during cutting.

More in detail, the peripheral slits <NUM> are preferably angularly equally spaced around the blade rotation axis A, and they preferably end into a hook-shaped segment.

In addition, the central disc <NUM> is preferably also provided with a plurality of preferably pass-through, inner slits <NUM> that are made in the central disc <NUM> at a given distance from the perimeter edge <NUM> and are specifically structured so as to damp the vibrations transmitted inside the central disc <NUM> during cutting operations.

More in detail, the inner slits <NUM> are preferably angularly equally spaced around the blade rotation axis A, and are preferably shaped like an S or a winding line.

Preferably the inner slits <NUM> are finally filled with a polymeric material preferably of elastomeric type, which is adapted to increase the vibration damping capacity of the inner slits <NUM>.

With reference to <FIG>, preferably the central disc <NUM> is moreover provided with one or more annular tensioning bands <NUM>, which are made on central disc <NUM> preferably via rolling, are spaced from central hole <NUM> and from perimeter edge <NUM>, and are adapted to locally stiffen the central disc <NUM> so as to reduce the twist and/or the vibrations of the disc blade <NUM> during cutting.

More in detail, the annular tensioning band or bands <NUM> are preferably located on the disc <NUM> at a distance from the blade rotation axis A preferably ranging between <NUM>% and <NUM>% of the value of the radius of central disc <NUM>.

With reference to <FIG>, finally the central disc <NUM> additionally has one or more balancing holes <NUM> that are preferably circular in shape, and are made in the body of central disc <NUM> in an eccentric position relative to the blade symmetry and rotation axis A, preferably along the periphery of the central disc <NUM>.

Preferably, the eccentric balancing hole or holes <NUM> are moreover of a pass-through type and/or have a diameter lower than <NUM> (millimetres) and, more conveniently, also lower than <NUM> (millimetres).

Furthermore, the balancing holes <NUM> preferably have all substantially the same diameter.

With reference to <FIG>, in addition, the eccentric balancing hole or holes <NUM> are preferably made close to the perimeter edge <NUM> of disc blade <NUM>.

More in detail, the balancing holes <NUM> are preferably made in the annular portion of central disc <NUM> extending between the perimeter edge <NUM> and the annular tensioning band or bands <NUM>.

In other words, the balancing hole or holes <NUM> are preferably made at a distance from rotation axis A greater than or equal to <NUM>% of the radius of central disc <NUM>.

More in detail, the balancing hole or holes <NUM> are preferably made at a distance from rotation axis A greater than or equal to <NUM>% of the radius of central disc <NUM>.

With reference to <FIG>, moreover the balancing holes <NUM> are preferably adjacent to one another and/or substantially equidistant from rotation axis A.

Preferably, the balancing hole or holes <NUM> are finally made in the periphery of central disc <NUM>, so that the distance of the balancing hole or holes <NUM> from the immediately adjacent peripheral slits <NUM> always exceeds a given limit, conveniently equal to <NUM>,<NUM>.

With reference to <FIG>, <FIG> and <FIG>, the machine <NUM> is adapted to make, in the body of central disc <NUM>, said balancing hole or holes <NUM> in one or more points of the disc periphery, so as to remove a quantity of material such as to balance the distribution of the masses of the disc blade <NUM> relative to the symmetry and rotation axis A of the blade.

Clearly, the number, dimension and/or position of the balancing holes <NUM> in the central disc <NUM>, or rather in the periphery of central disc <NUM>, depend/s on the initial position of the center of mass of the disc blade <NUM> relative to the symmetry and rotation axis A of the blade.

In other words, the number, dimension and/or position of the balancing holes <NUM> depend on the quantity of mass that needs to be removed from the central disc <NUM> in order to balance the disc blade <NUM> as best as possible.

More in detail, the number, dimension and/or position of the balancing holes <NUM> are determined so as to reduce and/or substantially eliminate the initial eccentricity of the center of mass of the disc blade <NUM> relative to rotation axis A.

Even more in detail, the number, dimension and/or position of the balancing holes <NUM> in the central disc <NUM>, or rather in the periphery of central disc <NUM>, are determined so as to bring the center of mass of disc blade <NUM> at a distance from the blade rotation axis A smaller than a predetermined maximum limit that is preferably function of the nominal or maximum rotation speed of the disc blade <NUM>.

Preferably, said limit value is furthermore lower than <NUM>,<NUM> (millimetres) and, more conveniently, lower than or equal to <NUM> (micrometres), i.e. <NUM>,<NUM>.

More in detail, the number, dimension and/or position of the balancing holes <NUM> in the central disc <NUM>, or rather in the periphery of central disc <NUM>, are determined so that the residual unbalance of disc blade <NUM> calculated according to standard ISO <NUM>-<NUM> falls within a given balancing grade (Gx) of standard ISO <NUM>-<NUM>.

In the example shown, in particular, the number, dimension and/or position of balancing holes <NUM> in the central disc <NUM> are preferably determined so that the residual unbalance of disc blade <NUM> calculated according to standard ISO <NUM>-<NUM> falls within a G100 balancing grade or lower, or more conveniently G40 or lower of the same standard ISO <NUM>-<NUM>.

Clearly, the balancing hole or holes <NUM> are made in the portion/sector of central disc <NUM> where there is, at beginning, an excess material that causes the unbalance. In addition, the balancing hole or holes <NUM> could also be blind holes, i.e. they could have a depth smaller than the thickness δ of central disc <NUM>.

In other words, some balancing holes <NUM> in central disc <NUM> can be blind holes and other balancing holes <NUM> can be through holes.

With reference to <FIG>, <FIG> and <FIG>, the disc-blade balancing machine <NUM> firstly comprises a self-supporting rigid structured <NUM>, which is preferably made of metal material and is adapted to stably rest on and optionally be firmly anchored to the ground.

The disc-blade balancing machine <NUM> additionally comprises: a blade-holder spindle <NUM>, which is fixed to the rigid structure <NUM> with the capability of freely rotating about a preferably substantially vertical, rotation axis B, and is adapted to support and rigidly lock the disc blade <NUM> while arranging it substantially coaxial to axis B, on a laying plane P perpendicular to the same axis; a preferably electrically-operated, motor assembly (not shown in the figures), which is adapted to drive the blade-holder spindle <NUM> into rotation about the axis B, preferably up to a predetermined angular speed ω; and an electronic detection device <NUM> that is located on the blade-holder spindle <NUM> and is adapted to detect a possible unbalance of the disc blade <NUM> fitted on the blade-holder spindle <NUM>.

More in detail, the electronic detection device <NUM> is adapted to detect and quantify the state of eccentricity of the center of mass of the disc blade <NUM> relative to the rotation axis B.

In other words, the electronic detection device <NUM> is adapted to detect the angular position of the center of mass of the disc blade <NUM> relative to a fixed reference and the distance of the center of mass of the disc blade <NUM> relative to rotation axis B.

In addition, the machine <NUM> is preferably also provided with an angular position transducer (not visible in the figures) which is fitted on the blade-holder spindle <NUM> and is adapted to detect, in real time, the angular position of the blade-holder spindle <NUM> relative to said fixed reference.

The motor assembly, in turn, is preferably structured so that it can vary, on command, the angular position of the blade-holder spindle <NUM> relative to the above-mentioned fixed reference.

With reference to <FIG>, in the example shown, in particular, the blade-holder spindle <NUM> is preferably provided with a preferably hydraulically- or pneumatically-operated, expansion locking head <NUM> which is adapted to fit and expand, on command, into the central hole <NUM> of disc blade <NUM>, so as to lock the disc blade <NUM> in rigid manner to the blade-holder spindle <NUM>, aligning at the same time the rotation axis A of the disc blade <NUM> to the rotation axis B of the blade-holder spindle <NUM>.

The electronic detection device <NUM>, on the other hand, preferably comprises a plurality of force transducers (not visible in the figures), which are adapted to measure the centrifugal force that the disc blade <NUM> temporarily fitted on the blade-holder spindle <NUM> transmits to the blade-holder spindle <NUM> when it is driven into rotation about the rotation axis B.

More in detail, the electronic detection device <NUM> is preferably provided with a plurality of piezoelectric accelerometers or similar sensors, which are grouped in one or more detection sets located along rotation axis B. The piezoelectric accelerometers of the or of each detection set are distributed around the blade-holder spindle <NUM>, on a same laying plane substantially perpendicular to axis B.

The use of a single set of sensors allows to detect the static unbalance of disc blade <NUM>. The use of two or more sets of sensors spaced along the rotation axis B allows to also detect the dynamic unbalance of disc blade <NUM>.

With reference to <FIG>, <FIG> and <FIG>, the disc-blade balancing machine <NUM> furthermore comprises: a preferably electrically-operated, drilling assembly <NUM> that is fixed to the rigid structure <NUM> beside the blade-holder spindle <NUM> and, preferably, also on a side of the laying plane P, with the capability of moving from and towards the laying plane P, so as to be able to reach and pierce, on command, the disc blade <NUM> temporarily fitted on the blade-holder spindle <NUM>; and a preferably electrically-operated, moving assembly that is adapted to move, on command, the drilling assembly <NUM> from and towards the laying plane P so that the drilling assembly <NUM> can reach and pierce the disc blade <NUM> temporarily fitted on the blade-holder spindle <NUM>.

More in detail, the drilling assembly <NUM> is preferably fixed on the rigid structure <NUM> above the laying plane P and, optionally, also in an eccentric position relative to the spindle rotation axis B.

Clearly, the drilling assembly <NUM> could also be located beneath the laying plane P.

The drilling assembly <NUM>, in addition, is preferably fixed on the rigid structure <NUM> so as to be able to move in straight manner from and towards the laying plane P in a given direction transversal to the laying plane P and, more conveniently, perpendicular to the laying plane P.

Hence, the drilling assembly <NUM> is adapted to reach/ intersect the laying plane P in one single predetermined point Q of the plane, so as to drill the disc blade <NUM> temporarily fitted on the blade-holder spindle <NUM> only in said point Q.

More in detail, with reference to <FIG>, <FIG> and <FIG>, the rigid structure <NUM> preferably comprises: a horizontal base <NUM>, on which the blade-holder spindle <NUM> is located; and a bearing column <NUM> that rises cantilevered from the base <NUM> parallel to the axis B, i.e. in a substantially vertical direction, beside the blade-holder spindle <NUM>, and is fixed to the base <NUM> with the capability of moving from and towards the blade-holder spindle <NUM> in a direction d<NUM> substantially perpendicular to axis B, i.e. substantially horizontal, preferably while remaining always parallel to itself.

In addition, the machine <NUM> is preferably also provided with a first, preferably electrically- or hydraulically-operated, actuator device <NUM> that is capable of moving, on command, the bearing column <NUM> from and towards the blade-holder spindle <NUM> in the direction d<NUM>, so as to vary/adjust the distance of the bearing column <NUM> from the axis B.

The laying plane P is preferably located above the base <NUM>, and the drilling assembly <NUM> is preferably fixed cantilevered on the bearing column <NUM>, with the capability of moving along the bearing column <NUM>, i.e. in a direction d<NUM> parallel to axis B, from and towards the base <NUM> and the laying plane P immediately above it.

In addition, the machine <NUM> is preferably also provided with a second, preferably electrically- or hydraulically-operated, actuator device <NUM> that is capable of moving, on command, the drilling assembly <NUM> along the bearing column <NUM>, in the direction d<NUM>, from and towards the base <NUM> and/or the laying plane P, so as to bring the drilling assembly <NUM> into contact with the disc blade <NUM> temporarily fitted on the blade-holder spindle <NUM>.

With reference to <FIG>, <FIG> and <FIG>, preferably the drilling assembly furthermore comprises <NUM>: a rotary tool-holder spindle <NUM>, which is firmly fixed to the rigid structure <NUM>, or rather to the bearing column <NUM>, with the capability of freely moving in the direction d<NUM>, and is adapted to receive and rigidly lock a drill bit <NUM> or other material removing tool; and a preferably electrically-operated, motor assembly <NUM> that is adapted to drive the tool-holder spindle <NUM> into rotation about its rotation axis C.

More in detail, the tool-holder spindle <NUM> is adapted to receive and rigidly lock the drill bit <NUM> or other similar tool, while placing the tool, or rather the drill bit <NUM>, locally coaxial to the spindle rotation axis C and locally parallel to the direction d<NUM>, i.e. parallel to axis B.

With reference to <FIG> and <FIG>, additionally the disc-blade balancing machine <NUM> also comprises: an electronic control device <NUM> which is adapted to drive/command the motor assembly of blade-holder spindle <NUM> and the moving apparatus of the drilling assembly <NUM> as a function of the data detected by the electronic detection device <NUM>; and preferably also an electronic blade-measuring device which is adapted to detect and communicate to the electronic control device <NUM> the diameter of the disc blade <NUM> temporarily fitted on the blade-holder spindle <NUM>.

More in detail, the electronic blade-measuring device is preferably located beside the blade-holder spindle <NUM>, and is adapted to detect the diameter of the central disc <NUM> of the disc blade <NUM> temporarily fitted onto the blade-holder spindle <NUM>.

The electronic control device <NUM> is adapted to command /control the motor assembly of the blade-holder spindle <NUM> so as to drive the blade-holder spindle <NUM> into rotation about the rotation axis B, and/or so as to vary the angular position of the blade-holder spindle <NUM> relative to said fixed reference, in order to vary/change the angular position of the disc blade <NUM> temporarily fitted onto the blade-holder spindle <NUM>.

Furthermore, the electronic control device <NUM> is adapted to drive/command the moving apparatus of the drilling assembly <NUM> so as to bring the drilling assembly <NUM> into contact with the disc blade <NUM> temporarily fitted onto the blade-holder spindle <NUM>. Preferably, the electronic control device <NUM> is moreover adapted to drive/command the moving apparatus of drilling assembly <NUM> also as a function of the data coming from said electronic blade-measuring device.

More in detail, the electronic control device <NUM> is provided with a data processing unit, which is adapted to determine/calculate, based on the data coming from the electronic detection device <NUM> and, optionally, also on the data coming from said electronic blade-measuring device, the position of the point or points of disc blade <NUM> where the balancing hole or holes <NUM> have to be made. In addition, the electronic control device <NUM> is adapted to also drive/command the motor assembly of blade-holder spindle <NUM> and the moving apparatus of drilling assembly <NUM> so as to make said balancing hole or holes <NUM> in the disc blade <NUM> temporarily fitted on the blade-holder spindle <NUM>.

Even more in detail, the electronic control device <NUM> is preferably programmed/configured to drive/command the motor assembly of blade-holder spindle <NUM> based on the signals coming from said angular position transducer, so as to align, time after time, a predetermined point of the disc blade <NUM> to the drilling assembly <NUM>, or rather to the drill bit <NUM>.

Preferably, the electronic control device <NUM> is moreover programmed/configured so as to automatically reject the disc blade <NUM> fitted on the blade-holder spindle <NUM> in case the number and/or the dimensions of the balancing holes <NUM> to be made exceed a predetermined limit threshold.

In addition, the electronic control device <NUM> is preferably adapted to also drive/command the first actuator device <NUM> so as to move, on command, the bearing column <NUM> from and towards the blade-holder spindle <NUM> in the direction d<NUM>. Furthermore, the electronic control unit <NUM> is preferably adapted to also drive/command the actuator device <NUM> so as to move, on command, the drilling assembly <NUM> along the bearing column <NUM>, in the direction d<NUM>, from and towards the base <NUM> and/or the laying plane P.

More in detail, the electronic control device <NUM> is preferably programmed/configured to drive/command the actuator device <NUM> based on the signals coming from one or more linear position transducers that are suitably located on the base <NUM> and/or on the column <NUM>.

Similarly, the electronic control device <NUM> is preferably programmed/configured to drive/command the actuator device <NUM> based on the signals coming from one or more linear position transducers that are suitably located on the column <NUM> and/or on drilling assembly <NUM>.

Preferably, the electronic control device <NUM> is furthermore adapted to also drive/command the motor assembly <NUM> of drilling assembly <NUM>.

The operation of machine <NUM> will be described below, assuming that the disc blade <NUM> to be balanced has already been fitted onto the blade-holder spindle <NUM>.

The balancing method implemented by the machine <NUM> comprises the steps of:.

Clearly, the number, position and/or dimensions (i.e. the diameter and/or the depth of the hole) of the eccentric balancing hole or holes <NUM> depend on the quantity of material that needs to be removed from the central disc <NUM> of disc blade <NUM> in order to bring the center of mass of the disc blade <NUM> in the neighbourhood of rotation axis A. In addition, the balancing hole or holes <NUM> can be blind holes of through holes.

Preferably, said maximum limit value is furthermore lower than <NUM>,<NUM> (millimetres) and, more conveniently, lower than or equal to <NUM> (micrometres), so as to fall within the G100 balancing grade of standard ISO <NUM>-<NUM> or, more conveniently, within the G40 balancing grade or lower of standard ISO <NUM>-<NUM>.

Preferably, the balancing method implemented by the machine <NUM> additionally comprises the step of automatically rejecting the disc blade <NUM> fitted on the blade-holder spindle <NUM> in case the number and/or the dimensions of eccentric balancing holes <NUM> to be made exceed a predetermined limit threshold.

In addition, the step of determining the initial position of the center of mass of disc blade <NUM> comprises the steps of:.

The step of bringing the disc blade <NUM> to be balanced into rotation about the rotation axis A furthermore comprises the steps of:.

Preferably, the disc blade <NUM> is furthermore driven into rotation by the blade-holder spindle <NUM> up to a given angular speed ω, preferably greater than or equal to <NUM> rpm (revolutions per minute).

In addition, after having made the balancing hole or holes <NUM>, the balancing method implemented by the machine <NUM> preferably also comprises the step of driving the disc blade <NUM> again into rotation about rotation axis A, so as to check whether the center of mass of the disc blade <NUM> is at a distance from rotation axis A smaller than said maximum limit value.

Preferably, on the other hand, the step of making one or more balancing holes <NUM> comprises the steps of:.

More in detail, the step of making the balancing hole or holes <NUM> in the central disc <NUM> of disc blade <NUM> comprises the steps of:.

In addition, in case a plurality of balancing holes <NUM> are needed for bringing the center of mass of disc blade <NUM> at a distance from rotation axis A smaller than said maximum limit value, the balancing method implemented by the machine <NUM> preferably additionally comprises, after having made the first balancing hole <NUM>, the steps of:.

Obviously, the balancing method implemented by the machine <NUM> entails repeating the steps listed above until the previously calculated number of balancing holes <NUM> is reached.

Clearly, the balancing of the disc blade can take place before and/or after the possible application of the tips or inserts <NUM> onto the teeth <NUM> of the disc blade <NUM>.

The advantages connected to the use of the disc-blade balancing machine <NUM> described above and with the balancing method implemented by it are remarkable.

First of all, the machine <NUM> makes the balancing of disc blades quicker and more economic, since it removes from central disc <NUM>, in a quick and completely automatic manner, the exact quantity of material needed to bring the center of mass of the blade in the neighbourhood of the rotation axis A.

In addition, the machine <NUM> does not require the correct balancing of the blade to be checked after every single material removal operation.

Furthermore, the machine <NUM> minimizes production waste because it calculates in advance and in a precise manner the number, position and/or dimensions of the balancing holes <NUM> to be made in the central disc <NUM> in order to balance the disc blade <NUM>, thus eliminating the risk of having to reject disc blades <NUM> at the end, due to an excess material removal.

The disc blade balancing method described above, in addition, does not require the presence of trained operators.

It is finally clear that modifications and variants can be made to the disc-blade balancing method and to the machine <NUM> described above without however departing from the scope of protection of the present invention that is defined by the appended claims.

For example, in a different not-shown embodiment, the eccentric balancing holes <NUM> could have a different cross section, such as for example an oval, elliptical, rectangular or similar cross section.

Claim 1:
A method for balancing of disc blades (<NUM>) which comprise a central disc (<NUM>) and a series of protruding teeth (<NUM>) jutting out cantilevered from the perimeter edge (<NUM>) of the central disc (<NUM>);
the method comprising the steps of:
- determining the initial position of the center of mass of the disc blade (<NUM>) to be balanced with respect to its main axis (A);
- calculating/determining the number, the position and/or the dimensions of one or more balancing holes (<NUM>) eccentric with respect to said main axis (A) and necessary for removing an amount of material sufficient to bring the center of mass of the disc blade (<NUM>) to a distance from the main axis (A) less than a predetermined maximum limit value; and
- forming said balancing hole or holes (<NUM>) on the central disc (<NUM>) in an eccentric position with respect to said main axis (A);
said method being characterized in that the step of determining the initial position of the center of mass of the disc blade (<NUM>) comprises the steps of:
- bringing said disc blade (<NUM>) to be balanced into rotation about its main axis (A); and
- determining the state/degree of initial eccentricity of the center of mass of the disc blade (<NUM>);
in that the step of bringing the disc blade (<NUM>) to be balanced into rotation about its main axis (A) comprises the steps of:
- rigidly locking the disc blade (<NUM>) to be balanced on a blade-holder spindle (<NUM>) so that the main axis of the blade (A) is substantially coincident with the rotation axis of the spindle (B); and
- driving the blade-holder spindle (<NUM>) into rotation about its rotation axis (B), so as to bring the disc blade (<NUM>) into rotation about its main axis (A);
and in that the step of forming said balancing hole or holes (<NUM>) on the central disc (<NUM>) comprises the steps of:
- stopping the blade-holder spindle (<NUM>) at least in a first previously-calculated angular position, so as to align a predetermined first point of the central disc (<NUM>) to a drilling assembly (<NUM>); and
- driving/commanding a moving apparatus of the drilling assembly (<NUM>, <NUM>) so as to form a balancing hole (<NUM>) at said predetermined first point of the central disc (<NUM>).