According to a particular aspect, the present invention relates to a machining centre for machining the ends of furniture parts and the like.

According to a further aspect, a subject of the present invention is a head for machining ends of furniture parts and the like.

A known type of tenoning machine for machining the ends of furniture parts comprises, basically, a head provided with a rotary tool. The known head has a box- like structure comprising kinematic chains connected to a drive device. The kinematic chains enable the machining movements of the tool to be performed along a predetermined path. For example, it is possible to move the tool along a circular or elliptical path in order to form tenons at the ends of the parts. Naturally, in order to produce the seats or mortises for coupling with the above-mentioned tenons, as well as to perform other

machining operations which are necessary to complete the furniture parts, at the moment, a plurality of machines having milling, drilling and polishing heads, respectively, are required.

In the particular case of the above-mentioned known tenoning machines, the kinematic chains which move the tool during the machining are arranged around the tool and make the head particularly bulky. This bulky head can be set in position by means of large guides which, owing to their dimensions, are complex, bulky and inaccurate. Moreover, because of the various devices fixed to the structure for supporting and moving the tool, such as apparatus for gripping the part, the movements of the box-like structure of the head are very limited, resulting in a correspondingly limited machining space in currently available machines. In addition to the foregoing, known tenoning machines require the tool to be replaced for each successive different type of machining operation and therefore increase the time required to produce the finished product.

The problem of the present invention is to propose a tenoning machine, a machining centre, as well as a head for machining ends of furniture parts and the like, which have structural and functional characteristics such as to overcome the disadvantages mentioned with reference to

the prior art.

This problem is solved by means of a tenoning machine comprising a head supported by means for controlled movement along at least three perpendicular axes and having a chuck unit with at least three chucks supported by the head in a manner such that the chuck unit can rotate about an axis and can at least reach a setting position with each chuck of the chuck unit, the head also having angular setting means, connected to the chuck unit with at least three chucks, for rotating the chuck disposed in the setting position about a first axis and a second axis which are perpendicular to one another and extend through the end of a tool held by the chuck.

Similarly, the technical problem is solved by the provision of a machining centre comprising two of the above-mentioned tenoning machines arranged facing one another.

Moreover, the technical problem is solved by the provision of a head to be fitted on one of the above- mentioned tenoning machines and comprising a chuck unit with at least three chucks supported by the head in a manner such that the chuck unit can rotate about an axis and can at least reach, with each chuck of the chuck unit, a setting position in which the chuck can be set angularly about a first axis and a second axis which are

perpendicular to one another and extend through the end of a tool held by the chuck.

For a better understanding of the invention, a non- limiting embodiment thereof is described below and illustrated in the appended drawings, in which: Figure 1 is a perspective view of a tenoning machine according to the invention, Figure 2 is a perspective view of a detail of the head of the tenoning machine of Figure 1, Figure 3 is a partially-sectioned perspective view of the detail of Figure 2, taken on the arrow III, Figure 4 is a perspective view of part-gripping apparatus facing a head, Figure 5 is a perspective view of a machining centre comprising two facing machines, Figure 6 is a partially-sectioned perspective view of the head of the tenoning machine of Figure 1, Figures 7 and 8 are partially-sectioned perspective views of further embodiments of a head for a tenoning machine according to the invention, Figure 9 is a partially-sectioned perspective view of the head of Figure 6, rotated through 180° about the axis B, Figure 10 is a perspective view of a further embodiment of a head for a tenoning machine according to

the invention, Figure 11 is a view showing the head of Figure 10 in section, from above.

With reference to the drawings, a tenoning machine for machining the ends of furniture parts is generally indicated 10.

The tenoning machine 10 comprises a base or framework 12 having longitudinal side members 14 supporting first parallel sliding guides 16 defining a first axis of movement (X-X).

A carriage 18 is coupled with the first sliding guides 16 by means of sliding shoes. The carriage 18 is operatively connected to first drive means 20 supported by the base 12. For example, a motor of the type known as a brushless motor is keyed directly to a screw housed in a female screw member with a recirculating-ball thread, fixed to the lower side of the carriage 18. The drive means 20 are operatively connected to an actuating device 22, operated in controlled manner. For example, the drive means 20 are operatively connected to a position transducer providing feedback to a numerical control device 23 operatively connected to the actuating device 22.

A pillar 24 extending vertically from the carriage 18 has, on one side, second parallel sliding guides 26

defining a second axis of movement (Z-Z). The pillar 24 has a C-shaped cross-section. The second guides 26 are fixed to the free ends of the arms of the C. The cavity formed by the arms of the C houses the service members of the tenoning machine 10 and the drive means for the upper axes described below.

Crossed slides 28 are operatively connected to the second sliding guides 26. The crossed slides 28 support a machining head, generally indicated 30. The crossed slides 28 comprise cross-members 32 having pairs of perpendicular sliding shoes 34 coupled, respectively, with the second sliding guides 26, and with third parallel sliding guides 36 fixed to a box-like or plate- shaped body 38 of the head 30 and defining a third axis of movement (Y-Y) (Figure 3).

The crossed slides 28 are operatively connected to second and third drive means 40 and 42 supported by the pillar 24 and by the box-like body 38 of the head 30, respectively. The drive means 40,42 are, for example, motors of the type known as brushless motors, keyed to screws housed in female screw members with recirculating- ball threads, fixed to the inside of the cavity in the C- shaped pillar and to the lower side of the box-like body 38 of the head 30, respectively. The drive means 40,42 are operatively connected to the actuating device 22,

operated in controlled manner. For example, position transducers operatively connected to the drive means 40, 52 provide feedback to the numerical control device 23 operatively connected to the actuating device 22.

A weight compensation device or counterweight 44 fixed to the pillar 24 is operatively connected to the crossed slides 28. For example, a pair of hydraulic or pneumatic cylinder and piston devices is fixed to the inner side of the cavity of the C-shaped pillar 24. The cylinder and piston device is operatively connected to the crossed slides 28 in a manner such as to counterbalance the effect of their weight and that of the head 30 operatively connected to the slides.

The head 30 comprises a yoke 46 extending from a shaft 48 housed in the box-like or plate-shaped body 38.

The shaft 48 is supported on the wall of the box-like body 38 remote from the pillar 24 by means of bearings 50 so as to rotate about a first setting axis (B), for example, coinciding with the axis of symmetry of the yoke 46. Drive means 52 are operatively connected to the shaft 48 so as to regulate the angular position of the yoke 46 about the axis (B). For example, a motor of the type known as a brushless motor 54 is connected to a pinion 58 by means of a transfer case 56 with a male and female screws, which is fixed to an internal wall of the

box-like body 38 of the head 30, the pinion 58 being connected, by means of a toothed belt 60, to a pulley 62 keyed to that end of the shaft 48 which is housed in the box-like body 38 of the head 30 (Figure 3). The drive means 52 are operatively connected to the actuating device 22 with feedback to the numerical control device 23 by means of a position transducer. A brake unit 64 subservient to the shaft 48 stops the rotation of the yoke 46 once the desired angular position about the axis (B) is reached.

In the vicinity of the free ends of shoulders 66, the yoke 46 has internal parallel channels 68 for slidably housing cradle-shaped or sector-shaped guides 70. The cradle-shaped guides 70 slide in the channels 68 of the shoulders 66 so as to swing about a second setting axis (A) perpendicular to the setting axis (B) of the yoke 46.

A chuck unit 72 with three chucks 72a, 72b, 72c is connected to the cradle-shaped guides 70 and is supported thereby in a manner such that the chuck unit 72 can rotate about an axis (D) perpendicular to the axis (C) of rotation of each chuck 72a, 72b, 72c (Figure 6). In particular, each chuck of the chuck unit can reach a so- called setting position corresponding, for example, to the position of the chuck 72a of Figure 1, in which the

axis (C) of rotation of the chuck in question is oriented towards the point of intersection of the first and second axes (B, A), defined as the centre 74 of the setting axes of the head 30.

The cradle-shaped guides 70 are operatively connected to drive means 76 fixed to a shoulder 66 of the yoke 46. For example, a self-braked motor 78 of the type known as a brushless motor is connected to a pinion 82, by means of a transfer case 80 with male and female screws fixed to the outer wall of the shoulder 66 and by means of a shaft housed in a bearing keyed in a through- hole in the shoulder 66. The pinion 82 is disposed inside the yoke 46 and is meshed with a rack 84 on a side of a cradle-shaped guide 70. The drive means 76 are operatively connected to the actuating device 22 with feedback to the numerical control device 23 by means of a position transducer.

Each chuck 72a-72c holds a tool 86, for example, a milling cutter 88 for producing tenons or mortises, a drilling bit 90, or a polishing pad. Particularly advantageously, the electric chuck holds the tool 86 in a manner such that the tool tip or zero point, that is, the end of the tool, coincides with the centre 74 of the setting axes (B, A) of the head 30 (Figure 2).

The chuck unit 72 is rotated about the axis (D), for

example, by the connection of the unit 72 to one of the cradle-shaped guides 70 by means of a planetary reduction gear 152 (Figure 9). The planetary reduction gear 152 enables the unit 72 to rotate about the axis (D) of the reduction gear 152 itself. The planetary reduction gear 152 is driven, by means of a pulley 154 fixed to its curved surface, by a belt 156 wound around a pinion 158 fixed to the shaft of a self-braking motor 160 supported on the side of the unit 72. The motor 160 is, for example, of the type known as a brushless motor and is operatively connected to the actuating device 22 with feedback to the numerical control device 23 by a position transducer.

Rotation of the unit 72 through 120° about the axis (D) of the planetary reduction gear 152 brings the second chuck 72b, and hence a second tool, to the position of use (at the centre 74 of the setting axes).

Moreover, as shown in Figure 11, the head 30 comprises, for each of the chucks, power-supply means for enabling the chuck to be rotated about its axis. In particular, the power-supply means comprise contact tracks 162 in the form of rings fixed to the unit 72 so as to be coaxial with the axis (D) of rotation of the unit 72. The power-supply means correspondingly comprise sliding contacts 164 arranged in contact with the tracks

and mounted on the head 30, more particularly, on one of the shoulders 66 of the yoke 46.

For easier fitting of the power-supply means, the head 30 may advantageously comprise a further yoke 166 fixed to the cradle-shaped guide 70 as shown in Figure 10. This embodiment provides for the shaft 48 housed in the box-like body 38 of the head 30 to support a bracket 150 in a manner such that it can be positioned angularly about the axis (B). The bracket 150 has, at its free end, a fixed guide 168 shaped as an arc of a circle. The cradle-shaped guide 70, which is in the form of a clamp fixed to the further yoke 166, is coupled with this fixed guide. In this embodiment, the rack 84 with which the pinion 82 meshes is on one side of the cradle-shaped guide 70, substantially as described for the embodiment of Figure 2.

Facing the head and subservient thereto is apparatus, generally indicated 92, for gripping the part.

The apparatus 92 for gripping the part is movable away from and towards the structure for supporting and moving the head 30. For example, the part-gripping apparatus 92 is supported by a portal structure 94. The portal structure 94 is connected to the sliding guides 16 on the base 12 by means of sliding shoes. For example, drive means 96 fixed inside the base 12 are operatively

connected to the lower side of the portal structure 94.

In particular, the means for moving the portal structure 94 comprise a self-braking motor 98 of the type known as a brushless motor, fixed to the base 12 and operatively connected to a screw 100 housed in a female screw member with a recirculating-ball thread fixed to the lower side of a base 102 of the portal structure 94. The motor 98 is operatively connected to the actuating device 22, with feedback to the numerical control device 23 by means of a position transducer.

A support plate 104 arranged transversely relative to the base 12 is cantilevered on the portal structure 94. The support plate 104 has a longitudinal slot 106 in which sliding guides 108 are housed.

A carriage 110 provided with a gripper 112 is operatively connected to the sliding guides 108. The carriage 110 is movable between a station 114 for the loading of the part 116 and a station 118 for the discharge of the part 116, passing through a machining station, under the action of operating means, generally indicated 120. The carriage 110 is supported on the sliding guides 108 in a manner such that the gripper 112 is disposed partially above an upper surface 122 of the support plate 104, which can constitute the surface for the support and sliding of the part 116. In particular,

the gripper 112 comprises a first, retractable, shoulder jaw 124 articulated to the carriage 110 and a second, clamping jaw 126 which is disposed facing the first jaw and is opened and closed selectively away from and towards the shoulder jaw 124 by means of a pneumatic device operable in controlled manner. The first jaw 124 comprises an abutment element or tip of synthetic material or rubber supported resiliently on the body of the first jaw 124. In the vicinity of the end of the carriage 110, facing the station 118 for the discharge of the part 116, there is a catch ejector 128. In the machining station, a seat provided in the support plate 104 partially interrupts the surface 122 for supporting and guiding the part. The seat houses a retractable catch 127 which is urged in the expulsion direction and is returned into the seat by a pneumatic device 129 operable in controlled manner.

Above the loading station 114, there is a vertical store 130 of known type. The store 130 comprises a device, synchronized with the to-and-fro movement of the gripper 112, for releasing the part 116.

In the machining station, which is disposed roughly on the centre line of the support plate 104, a device for clamping the part being machined is provided above the surface 122 for the support and sliding of the part 116

and is fixed to an upper cross-member 132 of the portal structure 94. For example, the clamping device is constituted by a small press or pressure member 134 comprising pneumatic cylinder and piston devices operable in controlled manner.

The operating means 120 for bringing about the to- and-fro movement of the carriage 110 will be described in greater detail below. The operating means 120 comprise a device with a connecting-rod 136 and a crank 138 connected to a splined bar 140 arranged longitudinally relative to the base 12 and supported thereon for rotating freely as a mechanical drive take-off spread along the base. In particular, the crank 138 is connected to a sleeve 142 with a splined profile slidable freely along the splined bar 140 so that it is always engaged therewith, irrespective of the position of the portal structure 94 relative to the base 12. The splined bar 140 is driven by means of an articulated quadrilateral device 144 connected to a geared drive unit 146 housed in the base 12. For example, the geared drive unit comprises an asynchronous motor connected to a reduction box, on the output shaft of which there is a crank with a link block, engaged with a connecting rod acting on a second crank operatively coupled to the splined bar. The ratios of the lengths of the arms of

the articulated quadrilateral 144. are selected in an appropriate manner such that the to-and-fro movement of the splined bar 140 takes place at different, speeds according to the angular arc travelled, in the manner described in greater detail below. The extreme angles of the rotary movement of the splined bar 140 correspond to the positions of the carriage 110 when it is positioned in the station 114 for the loading of the part 116 and in the station 118 for the discharge thereof. The asynchronous motor is controlled by an actuator, for example, a device commonly known as a inverter, so as to enable the carriage 110 to stop when it is in the machining station for sufficient time for the completion of the machining operations on the end of the part 116.

In one particular embodiment of the invention, the articulated quadrilateral is moved by means of a geared motor unit operatively connected to an actuator driven in controlled manner.

In a further embodiment of the invention, two apparatuses 92 are provided for gripping the part 116 and are slidable on the same base 12 so as to be movable separately towards and away from the head 30 in order to support the part 116 in the vicinity of its ends.

In an advantageous embodiment of the invention, two machines 10 for machining the ends of parts 116 are

arranged facing one another so as to act simultaneously on the two ends of the part, constituting a machining centre 148 (Figure 5). The two machines 10 are advantageously arranged for sliding on the same framework or base 12. Two apparatuses 92 for gripping the part are interposed between the two machines 10.

The operation of the tenoning machine 10, of the machining centre 148, and of the head 30 for machining the ends of furniture parts 116 is described below the reference to Figures 1, 4 and 5.

The part 116 to be machined is released from the vertical store 130 and is placed on the support and sliding surface 122 between the jaws 124,126 of the gripper 112.

The portal structure 94 supporting the apparatus 92 for gripping the part 116 is arranged along the base 12 beforehand in a manner such as to align the support plate 104 with the end of the part 16 to be machined.

As a result of a command imparted by the numerical control device 23, the gripper 112 is clamped onto the end of the part 116 and the carriage 110 is brought into the machining station beneath the clamping device by a rotary movement of the splined bar 140. During the last stages of the movement of the gripper 112 towards the machining station, the retractable catch 127 is moved out

of the seat in the support plate 104 by a command imparted to the pneumatic device 129 by the control unit 23. By virtue of suitable rules of movement imparted to the geared motor unit 146 by the inverter, after the carriage 110 has performed the stages of moving towards the machining station at high speed, it slows down so as to place the part 116 against the retractable catch 127 without an impact. The travel of the carriage then continues so as to preload the abutment element of the first, shoulder jaw 124 and to unload the second, clamping jaw 126, so that the gripper 112 can open after the part 116 has been clamped. When the part 116 has been clamped by the lowering of the press 134, the gripper 112 is opened and the carriage 110 is returned.

The catch ejector 128 moves under the part 116 clamped in the machining position and the carriage 110 returns to the station 114 for the loading of the parts 116.

Upon completion of the machining, whilst the carriage 110 brings a second part 116 to the machining position, the ejector 128 disposed on the end of the carriage 110 urges the part 116 which has already been machined and released from the action of the press 134 towards the unloading station 118.

When the part 116 is clamped in the machining position, the tenoning machine 10 is moved along the axis

(X-X) so as to bring the head 30 into the vicinity of the machining area. By virtue of the fact that the tool 86 is supported on the end of a yoke 46 which extends from the front of the box-like body 38 of the head 30, when the tool 86 reaches the machining point or the machining area, the structure for supporting and moving the head 30 and, in particular, the carriage 18 and the pillar 24, will be set back appreciably relative to the end of the part 116, permitting ample setting movements of the tool 86.

The unit 72 is rotated about the axis (D) in order to bring the chuck 72a and the preselected tool 86 into the setting position. The chuck and the tool 86 are set by adjusting the position of the unit 72 and of the corresponding chuck 72a by rotation (or slewing) of the yoke 46 about the first setting axis (B) and swinging (or pitching) of the cradle-shaped guides 70 about the second setting axis (A).

When the tool 86 has been arranged along the predetermined axis, the crossed slides 28, the box-like body 38, and the carriage 18 can be moved, by virtue of the controlled movement along the three perpendicular axes (X-X, Z-Z, Y-Y), so as to move the tool 86 along the desired path.

Both ends of the part 16 can be machined

simultaneously by virtue of the provision of the two facing machines 10 operating simultaneously in the machining centre 148.

It can be appreciated from the foregoing that one of the main advantages of the invention is that, by mounting a chuck unit with at least three chucks on the tenoning machine, it is possible to perform several machining operations such as, for example, milling, drilling, cutting, etc. Moreover, the presence of a chuck unit 72 enables more than one machining operation to be performed with a single positioning of the part, achieving very accurate machining and greater production flexibility and speed since the unit 72 simply has to be rotated to bring the preselected tool into the setting position.

In addition to the foregoing is the fact that the tool supported by one of the chucks of the unit is moved directly by virtue of the provision of means for angular setting about two perpendicular axes (B, A) extending through the end of the tool. The slewing and pitching movements of the unit enable the axis (C) of the tool which is in the setting position to be oriented extremely accurately relative to the end of the part to be machined.

In a further embodiment of the invention, the motor 54 for the axis (B) of the shaft 48 supporting the yoke

46 or the bracket 150, the motor 78 for the axis (A) of swinging of the cradle-shaped guides 70, and the motor 160 for the transverse pivoting axis (D) of the unit 72 are controlled continuously by the numerical control device 23 so that these axes can also be used as machining axes to produce ends of parts with spatially complex surfaces.

A further considerable advantage is that the machining movements are performed along linear axes (X-X, Z-Z, Y-Y) which, even though they have considerable dimensions, are very precise. Moreover, the fact that the electric chuck is disposed on the end of a yoke projecting over the machining area or space enables the structure for supporting and moving the head (the carriage 18 and the pillar 24), as well as the box-like body 38 of the head itself, to be set back considerably, allowing the tool a large degree of freedom of movement.

The tenoning machine of the invention is consequently much more compact than known machines for a given machining space or, conversely, there is a much larger machining space with the tenoning machine of the invention than with known machines, for given dimensions or overall size.

Further advantages are described below.

The end of the tool is not moved during the movement of the setting axes (A) and (B) so that the setting-up of the tenoning machine is simpler, quicker, and more precise, thus permitting good productivity for both large and small production batches.

The kinematic drive chains of the axes (X-X, Z-Z and Y-Y) are of simple and precise construction (motors operated in controlled manner and connected directly to screws with recirculating-ball threads without the interposition of any reduction gearing), permitting improved machining tolerances and extremely high accelerations and speeds of the moving parts.

The provision of an electric chuck enables fast rates of rotation of the tool to be used, permitting very accurate finishing of the part.

The structure for supporting and moving the head 30, comprising the carriage 18, the pillar 24 and the crossed slides 28, is very stiff and strong and, as a result, as well as because all of the axes (X-X, Z-Z, Y-Y) are controlled, its movements are very precise and quick.

By virtue of the structure of the means for supporting and moving the head and of the structure of the head itself, the tenoning machine of the invention is extremely flexible, enabling all of the machining operations to be performed on the ends of furniture parts

with a considerable variety in the shapes which can be produced, for example, milling operations and, in particular, tenoning and mortising of any form or shape, and channelling, as well as drilling and polishing.

Machining accuracy and flexibility are further increased by virtue of the provision of part-gripping apparatus which is independent of the structure for supporting and moving the head. In particular, the stresses induced by the repeated accelerations along the linear axes (X-X, Z-Z, Y-Y) are not transmitted directly to the part-gripping apparatus.

The part-gripping apparatus can be arranged in the most suitable position along the base in order to grip parts of complex spatial shapes.

The provision of a device for moving the gripper, comprising a rotary drive device rather than a reciprocating one as is suggested by the prior art, enables the part to be loaded and discharged with considerable speed.

Moreover, owing to the provision of an articulated quadrilateral for driving the splined bar, the grippers for positioning the part to be machined can be accelerated and slowed down from the loading station to the machining position and from the machining position to the discharge station, without interrupting the rotation

of the motor.

The provision of a portal structure enables the means for clamping the part to be arranged so as not to obstruct the machining head, increasing the machining space.

Naturally variants and/or additions to the above- described and illustrated embodiments may be provided.

Some possible variants of the head 30 and, in particular, of the chuck unit 72 are shown in Figures 7 and 8. In addition to the head of Figure 2, in which the respective axes of rotation of the three chucks 72a-72c intersect at a point defining the centre of the unit 72 and are arranged at 120° to one another, further embodiments in which the arrangement and/or the number of chucks varies are possible. For example, Figure 7 shows a unit 72 with four chucks 72a-72d the respective axes of rotation of which are arranged at 90° to one another.

Moreover, as shown in Figure 8, the unit 72 may comprise three chucks 72a-72c in which the axes of rotation of two chucks 72a, 72c intersect at a point defining the centre of the unit, whereas the axis of rotation of the remaining chuck 72b is tangential to a circle having its centre at the centre of the unit.

This latter embodiment in particular achieves considerable advantages, such as easier approach to the

part to be machined and quicker positioning, particularly during machining operations perpendicular to the longitudinal axis of the part. For example, this solution solves the problem of forming cavities in the end of the part, in particular in the case of legs to be coupled with tubular support structures of chairs, etc., in which the cavities must extend through the entire width of the part and must have longitudinal. axes perpendicular to the longitudinal axis of the part. This situation is in fact impracticable with machining heads as shown in Figures 2 and 7 since the head would be disposed over the part-gripping apparatus during the machining.

Moreover, for the movement of the cradle-shaped guides 70, it is possible to provide a worm screw connected to a motor fixed rotatably to a shoulder 66 of the yoke 46 and connected by tangential gearing to a rack with helical teeth formed on a side of a cradle-shaped guide 70. This prevents jamming of the drive means caused by the deposition of dirt or chippings on the rack.

Furthermore, for machining parts with considerable transverse dimensions, the retractable catch constituting the stop abutment of the machining station is housed in a seat provided in a bracket extending from the upper

cross-member 132 of the portal structure 94 towards the support plate 104.

As can be seen from Figures 6-9, the tool can be set angularly about a further, third axis (D). The shaft housed in the box-like body 38 of the head 30 supports the bracket 150 in a manner such that it can be set angularly about the axis (B). The bracket 150 has, at its free end, a channel housing a cradle-shaped guide 70 subservient to drive means 76, in the manner described above. As already described above, the chuck unit 72 is connected to the cradle-shaped guide 70 by means of a planetary reduction gear 152 (Figure 9). The planetary reduction gear 152 enables the electric chuck 72 to rotate about the axis (D) of the reduction gear 152. The planetary reduction gear 152 is driven, by means of a pulley 154 fixed to its curved surface, by a belt 156 wound around a pinion 158 fixed to the shaft of a self- braking motor 160 supported on the side of the chuck 72.

The motor 160 is, for example, of the type known as a brushless motor and is operatively connected to the actuating device 22 with feedback to the numerical control device 23 by means of a position transducer.

Rotation of the unit 72 about the axis (D) of the planetary reduction gear 152 brings the respective chucks to the setting position of use (at the centre 74 of the

setting axes). It is thus possible to perform more than one machining operation with a single positioning of the part, achieving good machining accuracy and greater production flexibility and speed.

In a further embodiment of the invention, the motor 54 for the axis (B) of the support shaft 48 of the yoke 46, or of the bracket 150, the motor 78 for the axis (A) of swinging of the cradle-shaped guides 70, and the motor 160 for the transverse pivoting axis (D) of the unit 72 are controlled continuously by the numerical control device 23 so that they can be used as machining axes to produce ends of parts with spatially complex surfaces.

For the axis (D), for example, the situation is that illustrated in Figure 6 in which the axis (C) of rotation of the chuck 7a during machining does not extend through the centre 74 of setting of the head 30.