DESCRIPTION

Technical Field

The present invention relates to the field of carving decoration on compact materials, such as wood or derivatives thereof, foam materials, resins and plastics, metals, non-ferrous metal alloys etcetera. More in particular the invention relates to an automatic system for carving decoration on preferably, although not exclusively, wood and derivatives thereof; the systems makes use of a robot or any other machine for positioning and moving in the space (Cartesian and anthropomorphic robots, numerically controlled pantographs and NC machines in general) with at least six degrees of freedom.

The invention also provides a carving tool to be used in said system.

State of the Art

Excluding wood pulp and resin molding, to date only one automated system is substantially known for carving decoration on wood products, which uses numerically controlled multi-axis machines with cutting tools. A cutting tool is a tool equipped with more cutting edges arranged around an axis of rotation; the motion thereof is substantially composed of a cutting rotary motion around the axis of rotation and an overall movement forward of the tool (i.e. of the tool axis of rotation) along the trajectory where material shall be removed.

The piece to be carved, for instance a wood beam to mold, is essentially put on a work table in a numerically controlled machine. The operating head with the rotary cutter moves according to programmed trajectories on the piece, where grooves are thus obtained of given depth and width according to the trajectories and the cutter dimensions.

This method allows to greatly speed the decoration steps up, but the quality result is not too much satisfactory. Namely, the groove shape is too much "regular" due to the chip removal type connected with the cutter rotation during processing. This is particularly true of the decorations with curved parts, parts "entering" the piece thickness or "exiting" from the piece. Namely, the cutters are not suitable to make particularly acute angles or shape unusual and asymmetrical grooves; this is only possible using cutters of different shapes and dimensions and moving them repeatedly along the same groove (but in this case again the results are unsatisfactory, as many "rows" are formed on the piece that shall be removed manually). In any case with the use of these NC cutting machines an "aesthetically acceptable" result can be only achieved by significantly re-working the decoration manually, thus losing the advantages deriving from automation.

Object and summary of the invention

An object of the present invention is to provide a carving decoration system for wood and derivatives thereof, foam materials, resins and plastics, as well as metals and non-ferrous metal alloys, that allows to speed up the carving step, with or without chip removal and to achieve an aesthetic finishing acceptable to the market.

A further object of the present invention is to provide a carving decoration system that allows to obtain numerous various decorative profiles, without the need for a great number of tools.

This and other objects, better explained below, are achieved through a carving decoration system comprising a carving tool, provided with a cutting edge, and automatic moving means which are equipped with a head for fixing the tool and are designed to perform at least four degrees of freedom for the tool, wherein the piece carving step comprises the tool being moved through said automatic moving means according to programmed trajectories on two- and three-dimensional surfaces of the piece; characteristically, the motion of the tool cutting edge is substantially linear, not rotary (i.e. without rotary motion around an axis passing through the tool), that is it essentially matches with the motion of the head for fixing the tool.

In practice, the tool does not rotate, as occurs in milling machines: it cuts the material through a substantially linear motion, obviously according to both curved and rectilinear trajectories; the cut is performed not through the highspeed rotation of the cutting edge, but simply through the movement thereof in the tool feed direction.

According to the invention, the workpiece is fixed with respect to a fixed external reference system (for instance with respect to the ground), whilst the tool moving means move with respect to this fixed external reference system and the workpiece.

Herein the term "carving" also refers to engraving and, more in general, to hollowing.

Carving is preferably performed through chip removal, but in some embodiments it is also possible without it.

Adequately, according to particularly advantageous preferred embodiments, the moving means preferably comprise an industrial robot or any other machine for positioning and moving in the space (Cartesian and anthropomorphic robots, numerically controlled pantographs and NC machines in general) carrying the tool device.

Preferably, during carving the moving means allow at least six degrees of freedom for the tool fixing head, and therefore for the tool. Preferably the moving means comprise an anthropomorphic robot and the tool fixing head is associated with the robot wrist.

Practically, the tool associated with the robot (or other NC device for positioning and moving in the space) through the fixing head has no cutting rotary motion (typical of the milling machines); the electronic management program(s) stored in the electronic unit for controlling the tool moving means (robot or other) direct the tool cutting edge so as to obtain a product according to the instructions coming for instance from a CAM (Computer Aided Manufacturing) system.

In this way, according to advantageous embodiments during carving the moving means allow changes in the tool inclination with respect to the surface to be carved.

Adequately, during carving the moving means allow the tool to translate and contemporaneously to change inclination; preferably the change in inclination occurs at least with the tool cutting edge coming out of the piece towards the surface being carved.

According to preferred embodiments, the tool comprises a stem for fixing to the tool fixing head and a cutting blade onto which the cutting edge is defined and which projects from the stem end opposite to that for fastening to the fixing head.

"Blade" refers to a body or a body portion having a lower thickness than the body main dimension, wherein the cutting edge is obtained along the body main extension.

The tool stem may be preferably in the shape of a cylinder or a prism.

The cutting blade may be shaped in various manner, according to the carving shape to be obtained.

The cutting edge, as well as its rake angles, can be sharpened in the most adequate manner for the material to be carved.

The cutting edge preferably lies on a plane.

According to preferred embodiments, the cutting edge lies on an inclined plane with respect to the main extension direction of the stem. In this way, when "attacking" the piece, the cutting edge immediately engraves the piece and subsequently removes the material, thus avoiding to chip the piece.

According to some preferred embodiments, with the tool substantially directed from the bottom upwards, with the cutting edge arranged at the bottom, the cutting blade comprises a lower part opposite to the stem extending from the lowest part of the cutting edge upwards substantially obliquely with respect to the stem extension. This avoids or reduces the risks of "tool-chip friction", i.e. the risk that, while carving, during the steps of tool inclination change, the rear of the blade (i.e. the part opposite to the cutting edge according to the cut direction) touches the piece when the tool is inclined with the cutting edge rotated upwards.

According to preferred embodiments, the blade with cutting edge extends from said stem towards the space at the side of the same stem, so as to substantially project laterally from the stem body. In practice, the blade is like an appendix at the side of the stem, substantially extending from the free end of this latter. In practice, according to another aspect, the blade with cutting edge extends preferably transversally to the main extension of the stem.

According to some preferred embodiments the cutting blade extends from the stem in a convex manner, with the convexity towards the piece to be carved, that is the blade has a convex lower surface downwards and a concave upper surface upwards, the front joining area of said lower and upper surfaces defining the tool cutting edge.

According to some preferred embodiments, the cutting edge is curvilinear, while according to other embodiments it is formed by a rectilinear segment or by a plurality of rectilinear segments or a plurality of curvilinear segments or a combination of rectilinear and curvilinear segments. According to an embodiment the cutting edge is formed for instance by two rectilinear segments forming a concavity, i.e. in the shape of letter V.

According to some preferred embodiments the cutting edge is asymmetric with respect to a plane orthogonal to the extension direction of the tool stem. According to other embodiments, the cutting edge is symmetric with respect to such plane.

According to some embodiments the cutting blade extends like the stem, the cutting edge being rectilinear and substantially parallel to the stem extension; preferably, when the tool is in vertical position the blade lower surface goes upwards in opposite direction with respect to the cutting edge, thus preventing the tool moving against the piece during the inclination upwards of the cutting edge.

The tool fixing head preferably comprises a base for fixing to the robot wrist for instance through threaded connections; on this base a housing is defined for a tool support device; with this housing reversible blocking means are associated for blocking the support device in the same housing.

The tool support device preferably comprises a shank designed to be housed and blocked in said housing; said housing is comprised of a semi-cavity surrounding the shank along one side and, at the opposite part of the semi- cavity, of a movable blocking portion connected with pushing means that move the movable portion from a position far away from the semi-cavity, to allow the shank to be inserted or extracted, to a position near the semi-cavity, so as to push against the shank when it is inserted in the housing.

The shank preferably has, on the part facing the movable portion, a toothed surface designed to match the surface of the housing movable portion going into contact with the same shank, that is in turn counter-toothed, with the shape of the teeth forming undercut areas to prevent the shank from being removed from the housing. The semi-cavity has preferably a semi-cylindrical shape and the shank has a cylindrical extension with a flattened part, onto which the toothed surface is obtained, at the side designed to go into contact with the housing movable portion.

Preferably the housing movable portion is guided by guides preferably orthogonal to the axis of the housing, such as pins, and is connected, preferably through a join, to a translation actuator (for instance a hydraulic cylinder) mounted on the base of the device, with actuating axis preferably parallel to said guides.

Preferably, on the top of the fixing shank there is a flange for connecting a tool changing apparatus, and on this flange there is a seat for blocking the tool.

According to some preferred embodiments, the seat for blocking the tool on the support device is obtained on a block arranged on a plate positioned on a counter-plate through regulating means for adjusting their transverse position.

According to some embodiments, the tool changing system comprises a magazine for tools already mounted on support devices and held by clamps coupling the support devices preferably in correspondence of said flange.

A further object of the invention is a tool to be used in this system, i.e. a tool comprising a stem for fixing to automatic moving means and a cutting blade onto which the cutting edge is defined and which projects from the stem end opposite to that for fixing to the fixing head.

"Blade" refers to a body or a body portion having a lower thickness than the body main dimension, wherein the cutting edge is obtained along the body main extension.

The tool stem may be preferably cylindrical or prismatic.

The cutting blade may be shaped in various manner, according to the carving shape to be obtained.

The cutting edge preferably lies on a plane.

According to preferred embodiments, the cutting edge lies on an inclined plane with respect to the main extension direction of the stem.

According to some preferred embodiments, with the tool substantially directed from the bottom upwards, with the cutting edge arranged at the bottom, the cutting blade comprises a lower part opposite to the stem extending from the lowest part of the cutting edge upwards substantially obliquely with respect to the stem extension.

According to preferred embodiments, the blade with cutting edge is limited between two opposite sides of the stem, i.e. the blade does not project laterally from the stem body. Preferably, the blade delimits a hole on the tip of the stem, defining said concavity towards the stem and part of the border of the hole forms the cutting edge. According to some preferred embodiments, the blade can be symmetrical with respect to the stem axis; preferably, the blade is a V or U -shape blade with a V or U-shaped cutting edge, with the axis Z intersects the blade at the vertex of the V or U shape. According to other preferred embodiments, the blade can be asymmetrical with respect to the stem axis; preferably the blade is a V-shape blade with a V-shaped cutting edge, the stem axis intersects the blade at a lateral portion of the blade; preferably, the vertex of the V-shape blade is aligned on one side of the stem.

According to preferred embodiments, the blade with cutting edge extends from said stem towards the space at the side of the same stem, so as to substantially project laterally from the stem body. In practice, the blade is like an appendix at the side of the stem, substantially extending from the free end of this latter.

According to some preferred embodiments the cutting blade extends from the stem in a convex manner, with the convexity towards the piece to be carved, that is the blade has a convex lower surface downwards and a concave upper surface upwards, the front joining area of said lower and upper surfaces defining the tool cutting edge.

According to some preferred embodiments, the cutting edge is curvilinear, while according to other embodiments it is formed by a rectilinear segment or by a plurality of rectilinear segments or a plurality of curvilinear segments or a combination of rectilinear and curvilinear segments. According to an embodiment the cutting edge is formed for instance by two rectilinear segments forming a concavity, i.e. in the shape of letter V. According to some preferred embodiments the cutting edge is asymmetric with respect to a plane orthogonal to the extension direction of the tool stem. According to other embodiments, the cutting edge is symmetric with respect to such plane.

According to some embodiments the cutting blade extends like the stem, the cutting edge being rectilinear and substantially parallel to the stem extension; preferably, when the tool is in vertical position, the blade lower surface goes upwards in a direction opposite to the cutting edge.

Brief description of the drawings

Further characteristics and advantages of the present invention will be more apparent from the description of a preferred, although not exclusive, embodiment, illustrated by way of non limiting example in the attached tables of drawings, wherein:

figure 1 is an overall schematic view of an anthropomorphic industrial robot in a carving decoration system according to the invention;

figure 2 is an axonometric view of the tool fixing head of the system according to the invention, with the tool and the corresponding support device being fixed to/released from the head;

figure 3 is an axonometric view of a tool magazine in a system according to the invention, wherein the tools are joined to the respective support devices shown in exploded view with respect to the magazine;

figure 4 is an axonometric view of a first embodiment of a tool of a system according to the invention;

figure 5 is a cross-sectional side view of the tool of figure 4 according to the plane V-V of figure 6, enlarged with respect to figure 4;

figure 6 is a top view of the tool of figure 4;

figure 7 is a top view of the tool of figure 4;

figure 8 is an axonometric view of a second embodiment of a tool of a system according to the invention;

figure 9 is a cross-sectional side view of the tool of figure 8 according to the plane IX-IX of figure 10, enlarged with respect to figure 8;

figure 10 is a top view of the tool of figure 8; figure 1 1 is a top view of the tool of figure 8;

figure 12 is an axonometric view of a third embodiment of a tool of a system according to the invention, shown at the back with respect to the cutting edge;

figure 13 is an axonometric view of another embodiment of a tool of a system according to the invention;

figure 14 is an enlargement of figure 13 relating to the cutting area of the tool;

figures 15a, 15b, and 15c respectively show two schematic side views and one schematic front view of the movement of the cutting edge of the tool according to the invention;

figure 16 is an axonometric view of a further embodiment of a portion of tool of a system according to the invention;

figure 17 is a front view of the embodiment of figure 16;

figure 18 is a side view of the embodiment of figure 16;

figure 19 is an axonometric view of another further embodiment of a portion of tool of a system according to the invention;

figure 20 is a front view of the embodiment of figure 19;

figure 21 is a side view of the embodiment of figure 19;

figure 22 is an axonometric view of a last further embodiment of a portion of tool of a system according to the invention;

figure 23 is a front view of the embodiment of figure 22;

figure 24 is a side view of the embodiment of figure 22.

Detailed description of an embodiment of the invention

With reference to the previously mentioned figures, number 10 indicates as a whole a system according to the invention carving or engraving decoration on wood and derivatives thereof, foam materials, resins and plastics in general, as well as on non-ferrous metal alloys. This system comprises automatic moving means for moving a carving tool, that are preferably embodied by an industrial robot 1 1 , for instance of the anthropomorphic arm type (i.e. the degrees of freedom are preferably obtained by means of rotational joints) preferably with six degrees of freedom, for instance formed by the hinge axes X of the various articulated parts, as shown in figure 1 , and in particular the vertical axis X1 of rotation of the base 1 1 A of the robot 1 1 , the horizontal parallel axes X2, X3 and X4 hinging the articulated parts 1 1 B, 1 1 C and 1 1 D, the axis X5 orthogonal to the axis X4, hinging the base 10E' of the robot "wrist" and the articulated part 1 1 D, and the axis X6, orthogonal to the axes X5 and X4, hinging the wrist base 1 1 E' and the wrist 1 1 E". This robot 1 1 is only schematically represented and is given just by way of non-limiting example of the invention.

Obviously, other examples of robots mat be provided, combining articulated systems and translating systems and more in general robots of the type with three main joints (i.w. the joints performing the main three degrees of freedom) that are a combination of rotoidal joints and prismatic joints (for translation). Examples of prismatic robots are for instance the Cartesian robots; rotoidal robots are for instance the anthropomorphic robots. "Mixed robots" are for instance the "spheric" robots (two rotations and one translation) and the "cylindric" robots (one rotation and two translations).

In the system according to the invention the degrees of freedom for the tool are conveniently at least four, and, as already said, preferably six degrees of freedom or more (i.e. three other degrees of freedom are added to the three main degrees of freedom).

A head 12 for fixing the carving tool 13 is fixed in a preset position to the wrist 10E" for instance by means a screw and/or bolt system.

In this example the head 12 for fixing the tool 1 3 comprises a base 14 for fixing to the robot wrist 10E"; on this base a housing 15 is defined for a support device 16 supporting the tool 13. Means 17 are associated with the housing for reversibly blocking the support device in the housing, as described below.

The support device 16 for the tool 13 comprises a shank 18 designed to be housed and blocked in the housing 15. Adequately, at the top of the fixing shank there is a flange 19 for connecting a tool changing apparatus, comprising a magazine 20 which is schematized in figure 3 and onto which there is a plurality of seats 21 for blocking the tool, embodied for instance by C-shaped clamps designed to surround elastically the devices 16 in correspondence of annular cavities obtained on the flanges 19. On the bottom of the seats 21 a tab 21 A is arranged to correctly position the device in the seat, designed to couple to a complementary imprint 21 B.

Adequately, the housing 15 for the shank 8 is formed by a semi-cavity 15A surrounding the shank along one side and, at the opposite part of the semi- cavity, by a movable blocking portion 15B connected with pushing means that move the movable portion 15B from a position far away from the semi-cavity, to allow the shank to be inserted or extracted (as in figure 2), to a position near the semi-cavity, so as to push against the shank 18 when it is inserted in the housing 15.

In this example the semi-cavity 15A has a semi-cylindrical shape and the shank 18 has a cylindrical extension with a toothed flattened part 18A at the side designed to go into contact with the movable portion 15B of the housing 15 that, when closing, pushes on this flattened part 18A. A toothed surface 1 5B' is obtained also on the movable portion 15B; this surface faces the semi-cavity and therefore the shank 18, when it is inserted in it. This toothed surface 15B' is complementary with the toothing 18A' defined on the flattened part 18A, in practice the toothing on this toothed surface 15B' has a shape of the teeth forming undercut areas to prevent the shank from being removed from the housing. The toothing 18A' and 15B' form part of the blocking means 17.

The blocking means 17 furthermore comprise the pushing means for pushing the movable portion 15B towards the semi-cavity 15A and more in particular, in this example, they comprise a translation actuator 22 (for instance a hydraulic cylinder) mounted on the base 14 of the head 12. The movable portion 15B of the housing 15 is guided by guides preferably orthogonal to the axis of the housing, such as pins 23, and is connected, preferably through a joint 24, to the translation actuator 22 (having actuating axis preferably parallel to the pins).

The tool 13 comprises a stem 25 for fixing to the fixing head 12, and a cutting blade 26 (better described below) onto which the cutting edge 27 is defined and which projects from the end of the stem opposite to the end for fixing to the head 12. In this example the stem 25 is mainly prismatic, but in other embodiments it may be mainly cylindrical, or a combination of cylindrical and prismatic solids or other shapes.

The tool 13 is arranged on the blocking device 16 inside a blocking seat 28 obtained on a block 29 arranged on a plate 30 positioned on a counter-plate 31 through regulating means for adjusting their transverse position, such as a guide 32 and a counter-guide 33 and blocking slots for bolts, not shown.

Figures 4 to 7 show a first embodiment of the tool 13. As already said, the tool has a stem 25 from which extends, at the end, a cutting blade 26 onto which the carving cutting edge 27 is defined.

"Blade" refers to a body or a body portion having a lower thickness than the dimension of the main extension of the body or of the portion, wherein the cutting edge is obtained along the body main extension.

Preferably, the blade 26 with cutting edge 27 extends from the stem 25 towards the space at the side of the same stem, so as to substantially project laterally from the stem body. In practice, the blade is like an appendix at the side of the stem, substantially extending from the free end of this latter. Therefore, the blade with cutting edge substantially extends preferably transversally to the main extension of the stem. The stem extension is substantially rectilinear, and is indicated by the axis Z.

In this example the cutting blade 26 extends from the stem 25 in a convex manner with the convexity towards the piece to be carved. (with reference to drawings in figures 4-7 the convexity is directed downwards). In practice, the blade 26 has a convex lower surface 26A and a concave upper surface 26B (facing upwards with reference to the drawings). The front area where the lower and the upper surface meet defines the cutting edge 27 of the tool; obviously, the sharpening surfaces of the cutting edge, for instance indicated with 27' and 27", are defined at the end of these lower and upper surfaces of the blade 26.

In this example the blade 26 forms a curve extending at the side of the stem. The cutting edge 27 is substantially a curvilinear segment, more preferably a segment shaped like an arc of a circle. The blade 26 preferably has a "conical" extension, i.e. the upper surface 26B has opposite portions 26B' tending to converge in a direction opposite to the cutting edge 27, i.e. in a direction opposite to the tool feed and cutting direction f.

Adequately, the cutting edge 27 lies on a plane P (in the example formed by a plane curvilinear segment), whose projection is indicated by the line, indicated by the same letter P in figure 5. This plane P is inclined with respect to the main extension direction Z of the stem 25 (angle a in figure 5). When the tool is directed substantially from the bottom upwards, with the cutting edge positioned at the bottom (as in the figures), the inclination of the plane P where the cutting edge 27 lies is such that the plane moves away from the stem 25 going upwards, i.e. in the direction of the cutting edge towards the semi-space occupied by the stem. In this way, when "attacking" the piece, the cutting edge 27 immediately engraves the piece and then removes the material, thus avoiding to chip the piece.

Always with the tool 13 substantially directed from the bottom upwards, and with the cutting edge arranged at the bottom, the cutting blade 26 comprises a lower part opposite to the stem, i.e. the surface 26A extending from the lowest part of the cutting edge upwards substantially obliquely with respect to the stem extension (inclination indicated by the angle β in figure 5) . This avoids or reduces the risks of "tool-chip friction", i.e. the risk that, while carving, during the steps of tool inclination change, the rear 26' of the blade (i.e. the part opposite to the cutting edge according to the cut direction) touches the piece when the tool is inclined with the cutting edge rotated upwards.

In this example the blade 26 (and therefore the cutting edge 27) is symmetric with respect to a plane parallel to the development of the stem 26. In other embodiments, it may be asymmetric according to the type of shaping to be obtained through carving. In practice, this plane of symmetry is parallel to the plane where the tool feed direction f lies.

The robot 1 1 allows automatically to move the tool 13 according to programmed trajectories on two- and three-dimensional surfaces of the piece to be carved. The electronic management program(s) stored in the electronic unit for controlling the robot (not shown in the figures) direct the tool cutting edge so as to obtain a product according to the instructions coming from a CAM (Computer Aided Manufacturing) system.

The movement of the cutting edge 27 of the tool 13 is substantially linear and not rotary, i.e. substantially matching the motion of the head 12 for fixing the tool 13, i.e. matching the movement of the wrist of the robot 1 1 . Obviously in some steps the tool may change inclination without cutting action or movement, that is a step where the cutting edge is correctly directed before starting a new cutting step (or before starting a new segment of a cutting trajectory).

To allow changes in the shape of the carving grooves, the robot therefore allows to change tool inclination with respect to the surface to be carved and this inclination change may occur also during the tool cutting motion, i.e. it may occur contemporaneously with the translation and inclination change of the cutting edge.

For example, a movement of translation and contemporaneous inclination change of the cutting edge, and therefore of the tool (practically corresponding to an overall movement of roto-translation of the cutting edge according to an axis not passing through the body of the tool) may correspond to a movement of entering, and then exiting from, the piece to be carved, with the tool moving forwards, inclining, attacking the piece, continuing moving forwards, inclining in opposite direction, exiting from the piece, practically with a "spoon" movement.

The inclination of the cutting edge is connected to its feed direction. In the example above the inclination has been described of the plane where the cutting edge lies with respect to the direction of extension of the tool stem. Preferably a main cutting horizontal direction f is defined (see figure 15) and, in the described example, during the cutting movement along this main horizontal direction the extension Z of the stem 25 is substantially vertical and the plane P where the cutting edge 27 lies is inclined as described. The inclination of the cutting edge is therefore linked to the cutting main direction f and is preferably defined by the angle a as angle between the plane P and the perpendicular to the cutting main direction f (that in the example matches the extension Z of the stem). Obviously, in other embodiments the stem with extension Z' of the tool may be not vertical (see figure 15b) during the movement according to the main cutting horizontal direction f and the cutting edge may maintain the inclination a as angle between the plane P and the perpendicular to the cutting main direction f (P and Z' will have therefore fixed inclination α').

The inclination changes of the cutting edge 27 may be obtained for instance by rotating the head 12 with the tool around the axis Z (according to φ in figure 15a), or by rotating the cutting edge on the plane orthogonal to the plane P where the cutting edge 27 lies (according to the angler π in figure 15a) or by rotating the cutting edge on the projection of the plane P on a plane where the axis Z lies (according to the angle ω in figure 15c).

Figures 8 to 10 show a second embodiment of the tool according to the invention, indicated with 1 13. In this example the blade, indicated with 126, projects laterally from the end of the stem 25 and has the same concavity/convexity as in the previous example; the only difference is that this is obtained through two incident planes with V-shape, and the cutting edge 127 is therefore formed in practice by two rectilinear incident segments 127A and 127B to form a concavity, i.e. V-shaped.

In this case again the cutting edge lies on an inclined plane with angle a with respect to the extension of the stem (as in the previous case) and the lower part opposite to the stem of the blade 126, i.e. the lower line 126' where the two planes 126A and 126B meet, moving upwards from the lowest part of the cutting edge in a substantially oblique manner (inclination indicated by the angle β in figure 9) with respect to the stem extension.

In this example again the blade 126 (and therefore the cutting edge 127) is symmetric with respect to a plane parallel to the extension of the stem 126 passing through the line 126'. In other embodiments, it may be asymmetric according to the type of shaping to be obtained through engraving. In practice, this plane of symmetry is parallel to the plane where the tool feed direction f lies.

In other embodiments the cutting edge may be formed by more curved segments in succession, or by more rectilinear segments in succession, or even by a combination of curved and rectilinear segments. For instance figure 12 shows a tool 213 wherein the cutting blade 226 is formed by a curved portion 226A and two plane portions 226B at the sides of the curved portion, in practice with a U-shape. Therefore, also the cutting edge 227 is formed, in succession, by a rectilinear segment, by a curved segment and by a rectilinear segment (or also by only a curved segment and a rectilinear segment).

In other embodiments (see figures 16-24), the blade with cutting edge is limited between two opposite sides of the stem 25, i.e. the blade does not project laterally from the stem body. In practice, the blade is like an appendix at the tip of the stem, substantially extending from the free end of this latter in the same direction of the development of the stem. Practically speaking, the stem axis Z intersects the blade.

Preferably, the blade delimits a hole H on the tip of the stem, defining said concavity towards the stem 25.

The blade can be symmetrical with respect to the stem axis Z. As an example, in the figures 16-18 a V-shape blade 426 with a V-shaped cutting edge 427 and inclination β (as defined above), is shown; the axis Z intersects the blade at the vertex of the V shape. In the figures 22-24, a U-shape blade 526 with a U-shape cutting edge 527 (formed by three rectilinear incident segments 527A-B-C to form a concavity) and inclination β, is shown.

The blade can by asymmetrical with respect to the stem axis Z. As an example, in the figures 19-21 , a V-shape blade 626 with a V-shaped cutting edge 627 and inclination β, is shown; the axis Z intersects the blade at a lateral portion 626A of the blade. As an example, the vertex 626C of the V-shape blade 626 is aligned on one side of the stem (a portion 626B of the V-shape blade 626 lays on the extension of one side of the stem).

Carving is preferably performed through chip removal, but in some embodiments it is also possible without it. For instance, figures 13 and 14 show a seventh embodiment of the tool, indicated as a whole with number 313, designed to carve mainly without chip removal. In this example the cutting blade 326 extends like the stem 25, with the cutting edge 327 (with sharpening surfaces 327') rectilinear and substantially parallel to the stem extension; preferably, when the tool is in vertical position, the blade lower surface 326B goes upwards in a direction opposite to the cutting edge, thus avoiding the problems of "tool-chip friction" during inclination of the cutting edge upwards. Preferably in this example the lower surface 326B of the blade is in practice a cutting edge connected with the lower corner of the cutting edge 327.

It is understood that what illustrated above purely represents possible non-limiting embodiments of the invention, which may vary in forms and arrangements without departing from the scope of the concept on which the invention is based. Any reference numbers in the appended claims are provided for the sole purpose of facilitating the reading thereof in the light of the description before and the accompanying drawings and do not in any way limit the scope of protection of the present invention.