FIELD OF THE INVENTION

The present invention relates to the technical sector concerning machine tools for precision mechanical working. DESCRIPTION OF THE PRIOR ART

To carry out precision mechanical machining operations, for example the machining of metal workpieces, it is known to use a machine tool which utilises specifically conformed tools for carrying out determined types of machining for transforming the shape and dimension of the workpieces to be machined. To fix the various tools to the machine tool, appropriate clamping devices are used. The clamping devices of a tool are then activated in rotation and translation by the machine tool, following particular movement motions, so as to move the tool with respect to the workpiece to be machined, according to the type of machining to be carried out. Clamping devices are known that realise the clamping of the tool following various modalities, for example by means of a hydraulic or mechanical clamping, or heat splining.

In particular, the present invention relates to a hydraulic clamping device of a tool for a machine tool. A known hydraulic clamping device of a tool is realised in the way described in the following.

The hydraulic clamping device of a tool comprises: a first part conformed to be fixed to a machine tool; a second part which comprises: a housing conformed to receive a tool predisposed to carry out a machining on a workpiece to be machined, which housing is in communication with outside by means of an opening and comprises lateral walls having at least a part made of an elastically deformable material; a hydraulic circuit containing a fluid; a pressure annular chamber which is arranged in such a way as to envelop the housing at least at the part made of an elastically deformable material of the lateral walls of the housing and which is in fluid communication with the hydraulic circuit.

Further, the known hydraulic clamping device of a tool comprises: fluid compression means for compressing the fluid contained in the hydraulic circuit so as to increase the pressure in the pressure annular chamber so that the at least a part made of an elastically deformable material of the lateral walls of the housing can expand in order to clamp a first tool inserted in the housing.

In detail, the fluid compression means comprise a presser element and a screw activatable to move the presser element.

The presser element is predisposed to be movable to intercept a tract of hydraulic circuit and thus to compress the fluid contained in the hydraulic circuit; while the screw is arranged in such a way as to be able to be set in rotation from outside, using a relative activating means (for example a screwdriver or the like), to push against the presser element so as to move it.

In other words, before the known hydraulic clamping device of a tool is activated in rotation and in translation to carry out, using the tool, the type of machining required on the workpiece to be machined, the tool will have to be inserted in the housing and, thereafter, the screw will have to be turned, using the relative activating means, which during the screwing action will push against the presser element to move it with the purpose of compressing the fluid contained in the hydraulic circuit, in such a way as to clamp the tool in the housing. In detail, during the machining of a workpiece to be machined, the machine tool is programmed to carry out multiple types of machining. Each machining can require a different tool, for example a tool for piercing, a tool for threading, a tool for trimming a tool for smoothing down a surface, a tool for bevelling the corners of a surface, etc. Therefore, with the aim of carrying out different types of machining on the same workpiece to be machined, with the known clamping device of a tool, it will be necessary to proceed with removal operations of the tool which is being used, by unscrewing the screw to free and replace the tool with another, which is apt for a different type of machining with respect to the preceding tool. Further, each time a tool is inserted in the housing it must be clamped in position before activating the hydraulic clamping device of a tool in rotation.

Thus, before activating the known hydraulic clamping device of a tool in rotation in order to clamp the tool in position internally of the housing an activating means is necessary to screw in the screw that is pushing against the presser element. These tool screwing-in and extracting operations require time and machine shutdowns, thus limiting the productivity of the machine tool itself.

In fact, if for example it were desired to make, on the workpiece to be machined, first holes and then a bevelling of the corners, with the known hydraulic clamping device of a tool, first it will be necessary to insert in the housing the tool predisposed to realise the holes and to screw in the screw to push against the presser element to move it, with the aim of compressing the fluid contained in the hydraulic circuit, in such a way as to clamp the tool in the housing so as to clamp the tool inserted in the housing so that it will be possible to activate the hydraulic clamping device of a tool in rotation to create the holes. Thereafter, to proceed with the bevelling of the corners, it will be necessary to pause the rotation of the hydraulic clamping device of a tool, unscrew the screw, remove the tool already present in the housing in order to fit a different tool predisposed to bevel and newly screw in the screw so as to clamp, in the same way as described in the foregoing, the tool in the housing so as to newly activate the hydraulic clamping device of a tool in rotation in order to bevel the corners of the workpiece to be machined.

SUMMARY OF THE INVENTION In the light of the above, the aim of the present invention consists in obviating the above-mentioned drawbacks.

The at least a rotary element pivoted to the second part of the hydraulic clamping device of a tool advantageously enables the at least a presser element to compress the fluid contained in the hydraulic circuit during the rotation of the hydraulic clamping device of a tool about the extension axis thereof, by effect of the centrifugal force which affects the at least a rotary element during the rotation of the clamping device.

Once the hydraulic clamping device of a tool is activated in rotation, the at least a rotary element by effect of the centrifugal force will rotate with respect to the fulcrum to press the at least a presser element so as to compress the fluid contained in the hydraulic circuit.

BRIEF DESCRIPTION OF THE DRAWINGS Specific embodiments of the invention will be described in the following part of the present description, according to what is set down in the claims and with the aid of the accompanying tables of drawings, in which: figure 1 and figure 2 are views in transversal section of the hydraulic clamping device of a tool, of the present invention, respectively in a rest condition and in an operating condition, when the first tool is in the first position; figure 1 A is a view of detail K of figure 1 ; figure 2A is a view of detail W of figure 2; figure 3 and figure 4 are views in transversal section of the hydraulic clamping device of a tool, of the present invention, respectively in a rest condition and in an operating condition, when the first tool is in the second position; figure 5 is a transversal view of the blocking device of the hydraulic clamping device of a tool, according to a second embodiment thereof; figure 6 is a view along plane VI-VI of figure 1 ; figure 7 is a view along plane VII-VII of figure 2; - figure 8 is an exploded view of the blocking device of the hydraulic clamping device of a tool of figure 1 .

DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference to the appended tables of drawings, reference numeral (1) denotes in its entirety a hydraulic clamping device of a tool for a machine tool.

A hydraulic clamping device (1) of a tool for a machine tool comprises: a first part (1 a) conformed to be fixed to a machine tool; a second part (1b) which comprises: a housing (2) conformed to receive a tool (5) predisposed to carry out a machining on a workpiece to be machined, which housing (2) is in communication with outside by means of an opening (2b) and comprises lateral walls (2a) having at least a part made of an elastically deformable material; a hydraulic circuit (3) containing a fluid; a pressure annular chamber (4) which is arranged in such a way as to envelop the housing (2) at least at the part made of an elastically deformable material of the lateral walls (2a) of the housing (2) and which is in fluid communication with the hydraulic circuit (3); fluid compression means (6) for compressing the fluid contained in the hydraulic circuit (3) so as to increase the pressure in the pressure annular chamber (4) so that the at least a part made of an elastically deformable material of the lateral walls (2a) of the housing (2) can expand in order to clamp a first tool (5) inserted in the housing (2) and predisposed to carry out a first type of machining on the workpiece to be machined.

Further, the fluid compression means (6) comprise: at least a presser element (6a) which is predisposed to intercept a tract of hydraulic circuit (3) and which is movable to compress the fluid contained in the hydraulic circuit (3); at least a rotary element (12) which is pivoted to the second part (1b), which is freely rotatable with respect to the fulcrum (13) and which is arranged so as to be in contact with the at least a presser element (6a) so that, when the hydraulic clamping device (1) of a tool is activated in rotation about the longitudinal axis (Y) thereof, the at least a rotary element (12) rotates about the fulcrum (13), by effect of the centrifugal force, so as to push on the at least a presser element (6a) and move it against the tract of hydraulic circuit (3) (see figures 1 -5).

The hydraulic clamping device (1) of a tool, object of the present invention, can be suitable for supporting at least a tool for carrying out a machining on a workpiece to be machined.

The hydraulic clamping device (1) of a tool can be of the tool-bearing type. In detail, the workpiece to be machined, during the movement of the hydraulic clamping device (1) of a tool, object of the present invention, i.e. when activated in rotation, is located externally of the hydraulic clamping device (1) so that the first tool (5) can carry out the machining thereon when supported by the same hydraulic clamping device (1). When the hydraulic clamping device (1) of a tool is activated in rotation about the longitudinal axis (Y) thereof, the first part (1a) and the second part (1b) are also activated in rotation with respect to the longitudinal axis (Y).

With particular reference to figures 1-5, the first part (1a) is arranged interposed between the machine tool (not illustrated) and the second part (1b). The first part (1 a) and the second part (1 b) can be adjacent to one another.

With particular reference to figures 1-5, the housing (2) extends internally of the second part (1 b) and along the longitudinal extension axis of the second part (1 b). The second part (1b) can comprise a first end (20) and a second end (21) which is opposite the first end (20).

The housing (2) can be arranged at the second end (21 ) of the second part (1 b). The second part (1b) can be connected to the first part (1a) by means of the relative first end (20).

The at least a part thereof made of an elastically deformable material of the lateral walls (2a) of the housing (2) can be such as to expand and retract inside the housing (2).

A part thereof made of an elastically deformable material of the lateral walls (2a) of the housing (2) can expand in order to abut and contact the first tool (5), when the first tool (5) is arranged in the housing (2).

The hydraulic circuit (3) can be a closed circuit.

The hydraulic circuit (3) can extend internally of the hydraulic clamping device (1) of a tool (see figures 1 -5). The fluid can be a hydraulic oil.

In detail, the pressure annular chamber (4) is arranged to envelop the at least a part thereof made of an elastically deformable material of the lateral walls (2a) (see figures 1-5).

The at least a presser element (6a) and the at least a rotary element (12) can be in a single body (not illustrated) or two separate bodies (see figure 8).

With particular reference to figures 6 and 7, the hydraulic clamping device (1) of a tool comprises three rotary elements (12, 12d, 12e) and three presser elements (6a, 6b, 6c). In detail, the three presser elements (6a, 6b, 6c) are predisposed to intercept different tracts of the hydraulic circuit (3) so that, when pushed by the three rotary elements (12, 12d, 12e), they are moved against the tracts of the hydraulic circuit (3) to compress the fluid contained in the hydraulic circuit (3) (see figures 6 and 7). The three presser elements (6a, 6b, 6c) are arranged in such a way that the relative axes of extension define an angle of 120° between them.

A balance is advantageously ensured between the weights borne by the hydraulic clamping device (1) of a tool.

In detail, figure 6 illustrates the rest condition in which the three presser elements (6a, 6b, 6c) are at rest and do not compress the fluid contained in the hydraulic circuit (3).

Instead, figure 7 illustrates the operating condition in which the three presser elements (6a, 6b, 6c) have been moved by the three rotary elements (12, 12c, 12d) so as to compress the fluid contained in the hydraulic circuit (3) in order to increase the pressure in the pressure annular chamber (4).

The considerations contained in this description for the at least a presser element (6a) and for the at least a rotary element (12a) are equally valid, in the same way, respectively, for the three presser elements (6a, 6b, 6c) and for the three rotary elements (12, 12c, 12d). The at least a rotary element (12) preferably comprises a first part (12a) and a second part (12b); the first part (12a) and the second part (12b) are arranged opposite with respect to the fulcrum (13); the second part (12b) has a smaller extension than the first part (12a) and is in contact with the at least a presser element (6a) (see figures 1-5).

The first part (12a) advantageously has a mass and volume such that it is affected by the centrifugal force to which the hydraulic clamping device (1) of a tool is subjected during the relative rotation about the longitudinal axis (Y) thereof.

In this way, the rotation of the at least a rotary element (12) about the fulcrum (13) determines the movement of the at least a presser element (6a) due to the thrust force exerted by the second part (12b).

The at least a presser element (6a) can be interposed between the hydraulic circuit (3) and the second part (12b) of the at least a rotary element (12).

The rotation axis (R) defined by the fulcrum (13) preferably lies on a plane which is arranged transversally to the plane on which the longitudinal extension axis (Y) of the hydraulic clamping device of a tool (1) lies.

This arrangement advantageously makes the hydraulic clamping device (1) of a tool compact and of modest size.

The second part (1b) is preferably conformed in such a way as to be able to support a second tool (8) predisposed to carry out a second type of machining on the same workpiece to be machined and the housing (2) is configured to receive internally thereof, in part or entirely the first tool (5) predisposed to carry out the first type of machining.

Further, the hydraulic clamping device (1) of a tool further comprises movement means (7) for moving the first tool (5) predisposed to carry out the first type of machining with respect to the housing (2) between a first position (P1), in which the first tool (5) projects from the opening (2b) towards the outside, so as to be able to carry out the first machining on the workpiece to be machined, and a second position (P2), in which the first tool (5) is situated in part or entirely internally of the housing (2) so that the second tool (8) can be able to carry out the second type of machining on the workpiece to be machined (see figures 1 , 3 and 5).

The movement means advantageously move the first tool (5), arranged in the housing (2), between the first position (P1), in which it projects from the opening (2b) towards the outside, to carry out the first type of machining on the workpiece to be machined and between the second position (P2), in which the first tool is situated in part or entirely internally of the housing (2), so that the second tool (8) can be made to carry out the second type of machining, different to the first type of machining, on the workpiece to be machined.

In other words, with the hydraulic clamping device of a tool (1) it is possible to carry out at least two different types of machining on a same workpiece to be machined, without having to wait for the removal and replacement times of the first tool (5) with the second tool (8), between one type of machining and another. Further, when the first tool (5) is in the second position (P2), the second tool (8) can carry out the second type of machining on the workpiece to be machined without the obstacle of the first tool (5), which is entirely arranged internally of the housing (2).

The first tool (5) and the second tool (8) can work separately on the same workpiece to be machined. By way of example, the first tool (5) can make holes, threads, or can bevel corners.

By way of example, the second tool (8) can be conformed to flatten a surface of a workpiece to be machined or to remove excess material from the workpiece to be machined.

The second tool (8) can comprise a second opening (8a) which can be crossed by the first tool (5), when the first tool (5) is in the first position (P1) (see figures 1 , 2 and 5).

The movement means (7) preferably comprise: a conduit (9) which is in communication with the housing (2); a fluid that can be fed into the conduit (9) in order to exert, on the first tool (5) arranged in the housing (2), a first thrust force so as to move the first tool (5) towards the first position (P1).

The movement means (7) advantageously moves the first tool (5) automatically by effect of the first thrust force exerted by the fluid, which fluid determines a movement of the first tool (5) towards the first position (P1 ).

Further, the movement means (7) ensure the movement of the first tool (5) without any need for manual operations.

The conduit (9) can be in communication with the first part (1a) (see figures 1-5) and the first part (1a) can be suitable for fixing to means for supplying a fluid (not illustrated) to be fed into the conduit (9).

The conduit (9) can comprise an end (9a) conformed to receive the first tool (5) so that, when the first tool (5) is situated entirely internally of the housing (2), a part of the first tool (5) can be received internally of the conduit (9) (see figures 3 and 4). The end (9a) of the conduit (9) and the housing (2) can form a cylindrical body and the first tool (5) can form a plunger so that the movement mechanism of the tool (5) with respect to the housing (2) is alike to that of a piston mechanism.

The fluid that can be supplied into the conduit (9) is preferably water. The fluid is fed into the conduit (9) at pressure.

The movement means (7) preferably comprise an abutment (10) arranged to abut the first tool (5), when pushed by the first thrust force exerted by the fluid, in such a way as to define an end-stroke abutment so that the first tool (5) is in the first position (P1) (see figures 1 and 2). At least a part of the first tool (5) advantageously remains arranged internally of the housing (2) and the part of the first tool (5) can be abutted by the at least a part thereof made of an elastically deformable material of the lateral walls (2a) of the housing (2), with the purpose of clamping the first tool (5) in the first position (P1). Further, the abutment (10) prevents the first tool (5) from involuntarily exiting the housing (2) by effect of the first thrust force.

The abutment (10) can be interposed between the conduit (9) and the housing (2). The abutment (10) can be step-formed.

In detail, with reference to figures 1-5, the abutment (10) is arranged between the end (9a) of the conduit (9) conformed to receive the first tool (5) and the housing (2).

The conduit (9) and the housing (2) can have the same extension axis. The first tool (5) can extend into the housing (2) along the same extension axis of the conduit (9) and the housing (2).

The movement means (7) preferably comprise a spring (11) which is interposed between an end of the first tool (5) and the abutment (10) in order to exert on the first tool (5) arranged in the housing (2), once the feeding of the fluid into the conduit (9) is interrupted, a second thrust force, having an opposite direction to the direction of the first thrust force, so as to move the first tool (5) towards the second position (P2) (see figures 3 and 4).

The spring (11) advantageously moves the first tool (5) automatically by effect of the second thrust force which it exerts on the first tool (5), determining a movement of the first tool (5) towards the second position (P2).

The second thrust force enters when the first thrust force is absent.

When the first tool (5) is subjected to the first thrust force and is positioned in the first position (P1), the spring (11) is completely compressed (see figures 1 and 2). When the first tool (5) is subjected to the second thrust force and is positioned in the second position (P2), the spring (11) is completely stretched (see figures 3 and 4).

The second part (1b) preferably comprises a removable portion (1c) which in turn comprises fastening means (1d) by means of which the fixing of the second tool (8) to the removable portion (1 c) takes place (see figure 8).

The second tool (8) can advantageously be removed from the second part (1b).

In this way it is possible to easily replace the second tool (8) with another, by operating on the fastening means (1d). At the moment of replacing the first tool (5) with another type of tool it is advantageously possible to decouple the second part (1b) and the removable portion (1c) from one another and remove the first tool (5) from the housing (2) (see figure 8). When the hydraulic clamping device (1) of a tool is activated in rotation about the longitudinal axis (Y) thereof, the removable portion (1c) is also activated in rotation about the longitudinal axis (Y), as it is fixed to the second part (1b).

The first part (1a) and the second part (1b) can be in a single body or be made in two bodies that are couplable to one another (see figure 8). The second part (1b) and the removable portion (1c) can be two bodies that are mutually couplable by coupling means (22) in turn comprising at least a screw (23) borne by the removable portion (1c) and a relative seat (24) fashioned in the second part (1 b) (see figure 8).

The hydraulic circuit (3) can comprise a first tract (3a) which extends internally of the second part (1b) and a second tract (3b) which extends internally of the removable portion (1c), which second tract (3b) is in direct fluid communication with the pressure annular chamber (4).

Further, the hydraulic clamping device (1) of a tool comprises a pair of pistons (15) arranged to connect the first tract (3a) and the second tract (3b) to one another so that the increase in pressure of the first tract (3a) of the hydraulic circuit (3) determines the relative movement of the pair of pistons (15) in order to increase the pressure of the second tract (3b) of the hydraulic circuit (3) (see figures 1 , 2, 1 A, 2A). When the second part (1b) and the removable portion (1c) are decoupled from one another, the pair of pistons (15) advantageously guarantees that there are no leakages of the fluid contained in the hydraulic circuit (3) at the joint point between the first tract (3a) and the second tract (3b) of the hydraulic circuit (3). In detail, when the fluid compression means (6) are activated, they compress the fluid contained in the first tract (3a) of the hydraulic circuit (3). This compression will cause the movement of the piston (15a) of the pair of pistons (15) arranged at the first tract (3a) of the hydraulic circuit (3) and, following the movement, the movement of the piston (15b) of the pair of pistons (15) arranged at the second tract (3b) of the hydraulic circuit (3) will be initiated.

The movement of the piston (15b) of the pair of pistons (15) arranged at the second tract (3b) of the hydraulic circuit (3) will cause, as a consequence, the pressure increase in the pressure annular chamber (4) (see figures 1 and 2A).

With particular reference to figures 1-5, these illustrate a first embodiment of the hydraulic clamping device (1) of a tool, when the first tool (5) is in the first position (P1) (see figures 1 and 2) and when the first tool (5) is in the second position (P2) (see figures 3 and 4).

Further, figure 1 and figure 3 illustrate a rest condition in which the first tool (5) is not clamped in position while figure 2 and figure 4 illustrate an operating condition in which the first tool (5) is clamped in position.

With reference to figure 5, this illustrates a second embodiment of the hydraulic clamping device (1) of a tool, object of the present invention, wherein the second part (1 b) comprises: a second housing (25) conformed to receive the removable portion (1c), which second housing (25) is in communication with outside by means of a third opening (25b) and comprises lateral walls (25a) having at least a part made of an elastically deformable material; a second hydraulic circuit (26) containing a fluid; a second pressure annular chamber (27) which is arranged in such a way as to envelop the second housing (25) at least at the part made of an elastically deformable material of the lateral walls (25a) of the housing (25) and which is in fluid communication with the second hydraulic circuit (26); a further presser element (28) which is predisposed to intercept a tract of the second hydraulic circuit (26) and which is movable by means of a further screw (29) to compress the fluid contained in the second hydraulic circuit (26).

In detail, by compressing the fluid contained in the second hydraulic circuit (26) an increase in pressure in the second pressure annular chamber (27) is determined so that the at least a part made of an elastically deformable material of the lateral walls (25a) of the second housing (25) can expand in order to clamp the removable portion (1c) inserted in the second housing (25).

The same considerations made in the foregoing in relation to the characteristics of the first embodiment can also be made for the second embodiment.

The following contains a description of a hydraulic clamping system (100) of a tool, comprising: a hydraulic clamping device (1) of a tool of any one of the above- mentioned embodiments; a first tool (5) which is arranged in the housing (2) and which is predisposed to carry out a first type of machining on a workpiece to be machined; a second tool (8) that is supported by the second part (1b) and which is predisposed to carry out a second type of machining on the workpiece to be machined.

By way of example, the following contains the functioning steps of the hydraulic clamping device (1) of a tool for realising a first type of machining and a second type of machining on a same workpiece to be machined, according to a first embodiment of the invention.

The functioning of the hydraulic clamping device (1) of a tool according to the second embodiment is the same.

By way of example, by first type of machining is meant the making of holes of the workpiece to be machined while by second type of machining is meant the removal of material of the workpiece to be machined.

Thus, on the basis of the foregoing, the first tool (5) inserted in the housing will be a tool suitable for making holes (see figures 1 and 2), while the second tool (8) supported by the second part (1b) will be a tool suitable for removing excess material (see figures 3 and 4).

Initially, the hydraulic clamping device (1) of a tool is connected to a machine tool by means of the first part (1a). For the purpose of realising the first type of machining by means of the first tool (5), the first part (1a) is connected to the means for supplying a fluid at pressure into the conduit (9) so that the fluid determines a first thrust force on the first tool (5) to move it into the first position

(P1) (see figure 1). During the movement of the first tool (5) into the first position (P1 ), the first tool will encounter the abutment (10) so that at least a part of the first tool (5) remains arranged internally of the housing (2) in which it is located (see figure 1). Once the first tool (5) is in the first position (P1), the machine tool activates the hydraulic clamping device (1) of a tool in rotation about the longitudinal extension axis (Y) thereof.

This rotation determines a centrifugal force which acts on the three rotary elements (12, 12c, 12d) determining a movement towards the outside of the relative first part (12a) of each of the three rotary elements (12, 12c, 12d) and, at the same time, a movement of the relative second part (12b) of each of the three rotary elements (12, 12c, 12d) against the corresponding three presser elements (6a, 6b, 6c) (see figure 2). The three presser elements (6a, 6b, 6c) are moved to intercept different tracts of the hydraulic circuit (3) with the aim of compressing the fluid contained in the hydraulic circuit (3) and consequently determining the increase in pressure of the pressure annular chamber (4) so that the at least a part thereof made of an elastically deformable material of the lateral walls (2a) of the housing (2) can expand towards the inside of the housing (2) to abut the at least a part of the first tool (5) arranged internally of the housing (2) to block the first tool (5) during the rotation of the hydraulic clamping device (1) of a tool (see figure 1). In this way, the first tool (5) is clamped in the first position (P1) for the whole duration of the first type of machining.

Thereafter, when the first type of machining is completed, the rotation of the hydraulic clamping device (1) of a tool will be halted so that the first tool (5) is no longer clamped internally of the housing (2). Following this, the supply of fluid under pressure into the conduit (9) will be halted and the first tool (5) will be moved by the second thrust force exerted by the spring (10) towards the second position (P2) (see figure 3). In the same way as described in the foregoing, once the first tool (5), by effect of the second thrust force, is entirely arranged internally of the housing (2) and in the end (9a) of the conduit (9) conformed to receive the first tool (5), i.e. the first tool (5) is in the second position (P2), the hydraulic clamping device (1) of a tool will be newly activated in rotation and the first tool (5) will be clamped in position, as previously described (see figure 4).

In this way, the second tool (8) can carry out the second type of machining on the workpiece to be machined.