EP2361173B1 - Device for manufacturing elongate rotationally symmetrical elements - Google Patents

Description

The present invention relates to a device for manufacturing parts of revolution according to the preamble of claim 1. Such a device is disclosed by DE 9209221 U1 .

Parts of revolution will be understood thereafter any piece of circular section, but also cross-sectional parts of generally elliptical shape or even, for some possible applications, of general polygonal shape, or twisted parts, etc..

By machining, it will be understood in general any method of forming by removal of material, whether by cutting tools, abrasive, etc..

The invention aims in particular, but not exclusively, the production of elongate wooden parts in a main axial direction, in particular axisymmetric, from long wooden bars. It can also be applied to the production of parts made of other materials, especially plastics, synthetic materials. The invention is particularly applicable to the realization, from a long bar, small parts section in relation to their length. It also applies to the production of larger parts by a machining transformation of a bar of typically square section, of any length, straight or curved, into parts of axisymmetrical section: circular, oval, square, possibly. helical, etc. variable longitudinal profile and respectively straight or curved.

Traditional turning devices are known for producing parts of revolution. In these devices, the bar to be machined is maintained by means of a mandrel with or without counterpaint or between points and is rotated about its axis. The machining of the profile to be achieved is then done by combining the movement, from one end to the other of the bar, of one or more tools and by the variation of the spacing of these tools relative to the axis. of the room. The variation of this spacing is generally performed either mechanically or by a numerical control system. However, these devices have several disadvantages. Indeed, the length of the workpiece is limited by the capacity of the machine. Traditional turning processes, although mostly automated, have a limited length capacity in general of 5 to 6 meters maximum for long length standards. The longer the part, the more the machine with this device is bulky and expensive. In the case of long and thin parts, there is a risk of bending or vibration at mid-length, which can generate unacceptable defects in machining quality. The turning process is by nature discontinuous, the loading and unloading of the machined part necessitating the stopping of the turning operation. It allows the realization of only one piece at a time. As a result, the efficiency of these devices is quite low, especially for heavy and bulky parts.

In addition, the sections made are necessarily circular, the parts must be straight. The production of parts such as for example twisted table legs, is more the special machine that filming and requires several successive operations. The turning of bent parts can only be achieved with the help of an expensive machining center, with long machining operations (programming, positioning of the part, machining, ...) hence a cost particularly high production.

Moreover, we already know, by DE9209221U1 or US4303111 processes, and manufacturing machines, based on the principle of rotating one or more tools around the machined part which remains fixed in rotation.

One of these known devices, for the manufacture of cylindrical posts, is composed of an electric motor which drives a hollow mandrel equipped with at least two blades oriented towards the center and uniformly distributed on the inside of the mandrel. The blades thus driven in rotation about the machining axis, allow to machine a workpiece along its axis and according to a fixed diameter defined by the position of the blades relative to the axis. This device makes it possible to machine long lengths of posts, but has several disadvantages. It allows the realization of only one piece at a time. Nor does it allow variations in diameter during machining. In addition, for each new diameter, reposition the blades and often disassemble and change the chuck according to the diameter to achieve. As a result, the efficiency of said device is very low, and the shapes of the products produced are limited to cylindrical shapes.

The document US1943649 describes a machine for making wooden poles such as telephone poles. This machine comprises a set of two tools driven in rotation along their respective axes, mounted on a plate which is itself driven in rotation about a main axis corresponding to the axis of the pole. The tools are arranged on the plate symmetrically opposite with respect to the axis of rotation thereof, and the radial distance between the axes of rotation of the tools and the axis of rotation of the plate can be adjusted by an on-board electric motor. the tray. It follows that this system uses a motor for rotating the plate, a motor for adjusting the radial position of the tools and a motor by tool for their rotation drive, four motors all on board the rotating part and thus requiring electrical commutators sliding contact for their power supply. The production of such collectors is complicated when the electrical current intensities are high. This also causes problems of electrical insulation and therefore safety. The size of these motors is important and moreover, these motors have a relatively large mass driven in rotation, and significant centrifugal forces result during the rotation of the plate. The reduction mechanisms used between the axial position adjustment motor and the tool supports do not allow rapid change of radial position of the tools.

The present invention aims to solve the problems mentioned above, and aims in particular to provide a device for machining on straight or curved bars of any length, parts of any circular section that any asymmetric, and according to a given longitudinal profile. It also aims to allow the use of such a device for making small parts in section, and having a small footprint. It is also aimed at providing a new machining device that enables continuous, high-speed machining capable of machining very thin bars, changing profiles instantly without changing tools, and machining closer to the maintenance. of the bar, thus eliminating the inevitable vibration and buckling effects during manufacturing by turning long pieces and small relative section. It also aims to provide a device also suitable for machining heavy and bulky parts such as profiled bars, poles beams and the like, obtained from bars of machinable material. Whether for small or large parts, the invention aims in particular the machining of soft materials, such as wood, especially balsa, cork and / or plastics such as polyurethane foam, up to hardwoods, resinous or not, such as beech or Ipe and other materials.

With these objectives in view, the subject of the invention is a device for producing parts of revolution according to claim 1.

Thus, the invention makes it possible to ensure a continuous variation of the radial position of the tools during the implementation of the device, and therefore during the rotation of the plate, without the need for this to use an on-board power unit on the board. this effect. The mass of the rotating parts can thus be reduced and the inertia and / or unbalance forces can be very reduced. In addition, it is not necessary to use a power supply by rubbing contact for such an onboard power plant.

Said mechanical transmission means comprise a set of bearings movable in the direction of the main axis, the bearing assembly comprising a first bearing driven in axial translation by said drive means and a second bearing rotatably connected with the rotating assembly. and in translation with the first bearing, the rotating assembly comprising mechanical connection means between the second bearing and the tool supports for converting the axial translation movement of the second bearing into radial displacement of the axes of the tools.

Each movable support is a lever pivotally mounted on the plate along a pivot axis parallel to the main axis, and said mechanical connection means comprise, associated with each arm, a reversible screw-nut assembly connecting the second bearing to the lever that an axial displacement of the second bearing relative to the plate causes a pivoting of the lever.

According to a particular embodiment, the reversible screw-nut system comprises, at its end connected to the lever, a pin eccentric relative to the axis of the screw-nut system and which engages in a groove formed at the end of a second arm of the lever. Preferably, the tenon is mounted eccentrically, so as to be able to adjust, by rotation of said pin on itself, the desired position of the corresponding lever as a function of the angular position of the end of the screw-nut system which carries it, in order to ensure a precise and identical radial positioning of the cutting tools.

According to another embodiment, the reversible screw-nut system comprises, at its end connected to the lever, a pinion engaging with a toothed sector formed on the lever.

Preferably, the nut of the reversible nut screw system is fixed on the second bearing, and the screw is rotatable, guided in rotation on the plate, and its end is connected to the lever.

According to another particular arrangement, the rotating assembly comprises rotational linking means linking in rotation the plate and the second bearing. These means of connection in rotation preferably comprise at least one rod integral with the plate and parallel to the main axis and sliding in a guide ring of the second bearing.

The rotating assembly is preferably rotated by a motor attached to the frame and connected to the turntable by a belt.

According to a particular embodiment, the motor means for controlling the displacement in axial translation of the first bearing comprise a fixed motor on the frame and the first bearing is driven in axial translation by a set of racks sliding parallel to the main axis and cooperating with pinions driven in rotation by said fixed motor.

Alternatively, the motor means comprise a fixed motor on the frame and the first bearing is a toothed nut having an internal thread engaged by screwing on a hub of the chassis centered on the main axis, the toothed nut cooperating with a pinion driven in rotation by said fixed motor.

The motor means could also include one or more actuators acting on the first bearing to move it in axial translation.

Each tool is preferably rotated on its support lever by a set of pulleys and belts connecting the tool to a drive roller held in rolling contact with a fixed inner ring secured to the frame. Thus, the rotation of the plate frictionally causes the rotation of the roller which in turn causes the rotation of the tool by the set of pulleys and belts. Typically, the roller is connected by a first belt to an intermediate shaft rotating in a bearing centered on the pivot axis of the tool support lever, and the shaft is connected to the tool by a second belt. Thus, the rotational drive of the tool can be assured regardless of the pivoting position of the tool support lever.

Furthermore, the roller is preferably rotatably mounted on a roller support arm pivotally mounted on the plate along the axis of pivoting of the tool support lever, so that the roller is firmly applied against the inner ring, and all the same. more strongly than the speed of rotation is higher, because of the centrifugal force then exerted on the roller bearing arm and the roller. A return spring may be arranged between the plate and the roller arm to ensure the contact without sliding between the roller and the ring even at low speed of rotation of the rotating assembly.

According to an alternative embodiment of the rotary drive of the tools, the device may comprise a rotary ring rotatably mounted on the chassis and driven in rotation by a third fixed motor on the frame, and the intermediate shaft comprises a wheel cooperating with said rotary ring so as to be rotated by the rotation of the rotary ring, and to rotate the tool, by a set of pulleys and belts, as in the previous embodiment. This arrangement is particularly suitable for the production of parts requiring a low speed of rotation of the plate, for example of the order of one turn per second, for non-circular section parts where the tools must move radially during the rotation of the tray. In such a case, the votation drive of the tools by a specific motor and by means of the rotary ring makes it possible to ensure a sufficient speed of rotation of the tools, despite the low speed of rotation of the rotating assembly. In general, this arrangement makes it possible to make the rotation speed of the rotating assembly and the speed of rotation of the cutting tools independent of each other.

Of course, the sets of pulleys and belts should be understood as also encompassing systems with toothed wheels and chains or other drive systems functionally equivalent and easily implemented by those skilled in the art. Similarly, the roller may be replaced by a pinion meshing with an internal toothing of the fixed ring. Also, the wheel cooperating with the rotary ring may be a toothed wheel in engagement with an internal toothing of this ring

Of all the characteristics which have just been indicated, taken in their various possible combinations, it will be understood that one of the main advantages of the invention is to allow the machining of parts of revolution, according to the definition which has given at the beginning of this description, from long bars of substantially square section, or rectangular, by rotating tools in an epicyclic movement around the said bar, and that by a device that does not require the use of embedded motors on rotating bodies. As a result, the rotating assembly is generally compact in order to minimize the centrifugal forces and thus reduce the weight of the rotating structures, their cost and the energy requirements necessary for their rotation. A motor located mainly outside the rotating structure allows to lighten the structure and, especially in the case of high rotation speed of the plate, reduce any unwanted vibrations. If necessary, however, it will be possible to use onboard motors for driving the tools in rotation, for example via the intermediate shafts mentioned above.

The rotary tools in the form of discs can be grinding wheels for machining parts made of soft material, such as, for example, balsa or cork, or synthetic foams, for example polyurethane. The replacement of grinding wheels by cutting tools allows the machining of softwood and / or hardwood, such as beech or Ipe, exotic wood. In general, the machining of any material is possible with ad hoc tools, the shape of the tools being determined so as to be able to make strong and rapid variations of sections according to the desired longitudinal profile.

The management of a phase shift of the section as a function of the advance makes it possible to produce helical shapes.

Other features and advantages will appear in the description which will be made of a machine according to the invention, as well as its implementation.

• les figures 1 et 2 sont illustration schématique du principe général de l'invention,
• - la figure 3 est une vue d'ensemble de la machine, en perspective vue du côté où la machine est alimentée par la barre à usiner,
• - la figure 4 est une vue d'ensemble de la machine, en perspective vue du côté arrière,
• - la figure 5 est une vue en perspective montrant l'ensemble tournant,
• - la figure 6 est une vue en 1/2 coupe axiale montrant la liaison en rotation entre le plateau et le deuxième palier,
• - la figure 7 est une vue en 1/2 coupe axiale montrant le mécanisme de commande du pivotement des leviers porte-outils,
• - la figure 8 est une vue en coupe du mécanisme d'entraînement en rotation d'un outil,
• - les figures 9 et 10 sont des vues en coupe axiale, respectivement selon les lignes IX-IX et X-X de la figure 11, d'une variante de réalisation de la machine, montrant respectivement les moyens d'entraînement en rotation des outils, et, en partie, les moyens de commande du pivotement des leviers support d'outil.
• - la figure 11 est une vue illustrant schématiquement le pivotement des leviers supports d'outils, représenté ici dans une autre variante de réalisation.

Reference is made to the accompanying drawings in which:

• the Figures 1 and 2 are schematic illustration of the general principle of the invention,
• - the figure 3 is an overview of the machine, in perspective seen from the side where the machine is fed by the bar to be machined,
• - the figure 4 is an overview of the machine, in perspective seen from the back side,
• - the figure 5 is a perspective view showing the rotating assembly,
• - the figure 6 is a view in half axial section showing the connection in rotation between the plate and the second bearing,
• - the figure 7 is a view in half axial section showing the mechanism for controlling the pivoting of the tool-carrying levers,
• - the figure 8 is a sectional view of the mechanism for rotating a tool,
• - the figures 9 and 10 are views in axial section, respectively along the lines IX-IX and XX of the figure 11 of an embodiment variant of the machine, respectively showing the means for rotating the tools, and, in part, the means for controlling the pivoting of the tool support levers.
• - the figure 11 is a view schematically illustrating the pivoting of the support levers of tools, shown here in another embodiment.

The patterns of Figures 1 and 2 illustrate the general principle of the invention. A bar B, of square section, is held fixed in rotation and machined by rotary cutting tools 3 driven in rotation on their axes A2 according to the arrows R1. the axes of the tools being themselves driven in rotation along the arrow R2 around the main axis A1 of the machine. The bar B is moved in translation along the main axis A1 of the machine, in the direction of the arrow F1, the advance of the bar being provided in a manner known per se by a drive system and a motor, not shown. .

The kinematics of the machine therefore consists in associating the translational movement F1 of the bar B to be shaped with a rotational movement R2 of the axes A2 of the tools 3 around the bar B.

The machine comprises a rotating assembly 4 comprising a plate 41 which supports the two cutting tools 3 diametrically opposed. Each tool can move radially relative to the main axis A1 of the machine, as will be seen later.

As will have already been understood, according to the invention, the bar B does not turn on itself. It is only subject to a longitudinal displacement, in its axial direction, through a guide piece 2. As soon as the output of the guide piece 2, said bar B is brought into contact with the tools, for example abrasive or cutting discs 3, each held on a tool holder rotated around said bar. From the exit of the guide piece, the bar is machined by the two tools 3 diametrically opposed to the main axis A1 which is also the axis of the bar. Both tools 3 are located in the same section plane located closest to the guide piece 2, which distributes the cutting forces on both sides of the bar B and limits the bending forces on it.

The spacing of the tool holders can be piloted by a numerical control which will then realize the profile of the part previously stored in a computer file.

A machine according to the invention will now be described in more detail.

The machine represented Figures 3 to 8 comprises a frame 1 on which is fixed rigidly a bell 11 inside which is mounted a rotating assembly 4 driven in rotation by a first motor 91. The rotating assembly 4 comprises in particular a plate 41 secured to a hub 42 guided in rotation on a bored rocket 12 integral with the frame and such that the bar B can pass axially in the bored rocket.

The plate 41 carries two movable tool holders consisting of levers 5 mounted diametrically opposite and symmetrical with respect to the main axis A1. Each lever 5 is pivotable along an axis A3, parallel to the main axis A1, in a through bore 411 of the plate 41. The lever 5 comprises a first arm 51 on the end of which is rotatably mounted the tool 3. The lever 5 comprises a second arm 52, inclined relative to the first arm 51 by an angle of, for example, approximately 100 °, as can be seen figure 5 . The two levers 5 are facing so as to leave free between them a space of suitable shape and dimensions, sufficient for the passage of the bar B during machining. A drive roller 61 is rotatably mounted on the end of a roller support arm 6 which is also pivotally mounted in the bore 411 of the plate 41. The roller 41 is held in contact with the inner surface 131 of a 13 ring device integral with the bell 11, for example by a spring not shown. The stone 61 is connected in rotation by a first set of pulleys and belts 62 at one end of an intermediate shaft 63 passing through the roller bearing arm 6 and the lever 5 and guided therein along their common pivot axis A3. The other end of the intermediate shaft 63 is rotatably connected by a second set of pulleys and belt 64 to the tool 3. Thus, when the roller 61 is rotated by friction with the ring 13 when the plate 41 rotates it transmits its rotational movement to the intermediate shaft and then to the tool 3, without requiring additional specific motor.

To ensure the radial displacement of the tools, the machine comprises a fixed motor 92 on the frame which drives by belts 71 of the pinions meshing with racks 72 sliding in the frame parallel to the main axis and integral with a first bearing 73 centered on the main axis A1. This first bearing 73 forms with a second bearing 74 an assembly 7 of two bearings guided in rotation on one another and linked in translation, so that the assembly 7 is movable in translation in the direction of the main axis , the first bearing 73 being fixed in rotation relative to the chassis because of its rigid connection with the racks 72, and the second bearing 74 according to the axial displacements of the first bearing and the racks, but being able to rotate relative to the chassis according to the axis A1. The second bearing is connected in rotation with the plate 41 by pins 44 secured to said plate, extending parallel to the axis A1 and mounted sliding axially in guide rings 75 integral with the second bearing. Other means of guiding in axial translation and rotational connection between the second bearing 74 and the plate 41 could also be used. The plate 41 is rotated by the motor 91, for example by a belt 911, and therefore in turn rotates the second bearing 74.

Furthermore, the second bearing 74 is also connected with the plate 41 and more particularly with two rotary cams 54 carried by this plate, by reversible screw-nut systems comprising a nut 77 rigidly fixed to the second bearing 74 and a screw 76 of which the end is guided in rotation on the plate 41 and carries a said cam, so that an axial displacement of the second bearing causes a rotation of the screw and thus the cam 54. The cam 54 carries a pin 541 which cooperates with a groove 521 formed in the end of the second arm 52 of the lever 5, so that a rotation of the screw 76 and the cam 54 causes a pivoting of the lever 5, and consequently a radial displacement of the tool 3.

• Une barre B à usiner est amenée selon la direction axiale A1 vers les outils. Le moteur 91 entraîne en rotation autour de l'axe principal A1 le plateau 41 et donc les leviers porte-outils 5 et les outils 3. Cela provoque la rotation des galets 61 par friction sur la couronne 13 et, comme indiqué précédemment, la rotation des outils sur leurs propres axes A2.

The operation of the machine is as follows:

• A bar B to be machined is fed in the axial direction A1 to the tools. The motor 91 drives in rotation around the main axis A1 the plate 41 and therefore the tool-carrying levers 5 and the tools 3. This causes the rollers 61 to rotate by friction on the ring 13 and, as previously indicated, the rotation tools on their own axes A2.

To vary the radial distance between the tools 3 and the bar B, and thus vary the machining radius, it controls the pivoting of the levers 5 by means of the motor 92, which causes the sliding of the racks 72 and the axial displacement of the set of bearings 7, which causes a rotation of the screws 76 and cams 54, and finally the pivoting of the levers 5.

Note that the use of a lever as described above to adjust the radial positioning of the tools allows a high clearance of the tools thanks to the reduced size of the support lever, and a high reactivity, necessary for the manufacture of small parts in series or for the realization of non-circular sections in the case of small rotations of the plate, and this without increasing the centrifugal force generated by the device because of the small masses induced by this lever system.

To precisely adjust the exact radial positions of the tools, and correct any distance difference between each of the tools and the main axis A1, taking into account any differences in the diameter of the tools or other dimensional dispersions of the parts of the mechanism, the tenon 541 is an eccentric which thus makes it possible, by rotating it on itself, to adjust the pivoting position of the lever 5 with respect to the rotational position of the cam 54.

In the embodiment of figures 9 and 10 , the rotation of the tools is carried out independently of the rotation of the plate 41, using a third motor 93 fixed to the frame and which rotates a ring 81 rotatably mounted on the frame along the axis A1. The rotation of each tool 3 is obtained thanks to a pinion 82, carried by an intermediate shaft 63 'guided in rotation along the axis A3 on the turntable 41, and the pinion 82 rolling on the internal toothing of the ring gear 81. The rotation of the pinion 82 and the intermediate shaft 63 'is transmitted to the tool by a system of pulleys and belts 83, similarly to that of the first embodiment.

In this second embodiment also, the system of axial displacement by rack of the bearings used to control the pivoting of the tool-carrying levers 5 is replaced by a toothed nut system in which a toothed nut 85 constituting the first bearing of the the set of bearings 7, is screwed on the rocket 12 and rotated by a pinion 86 itself driven by the motor 92. The rotation of the motor 92 causes the screwing or unscrewing of the toothed nut 85, and therefore its axial displacement on the rocket. This displacement is transmitted to the second bearing 74, and thence, as in the first embodiment, to the reversible screw-nut systems and to the tool-carrying levers.

The figure 11 illustrates a variant of the control of the pivoting levers 5 by the screws 76 reversible screw-nut systems. In this case, the end of the screw 76 carries a gear 58 which meshes with a toothed sector 59 made on the lever 5.

The invention can also be applied to the production of non-axisymmetric parts, for example by controlling the radial positioning of the tools in a different manner for the two tools. Such an arrangement may for example be implemented using an onboard electric motor specific to each tool, to adjust the positioning of the tools independently of one another. Care should be taken not to create excessive imbalance of the machine, limiting the speed of rotation of the tool support around the machined bar.

Claims (14)

1. Device for manufacturing elongated rotational parts, made of wood in particular, with a variable cross-section according to the longitudinal direction, by machining a bar (B) held fixed in rotation, the device including a fixed chassis (1) supporting guide systems (2) to guide said bar in translation along a main axis (A1) and hold it fixed in rotation, a rotary assembly (4) driven in rotation with respect to the chassis around the main axis, the rotary assembly including a platen (41) and at least two rotary tools (3) supported by moving supports formed by levers (5) mounted pivoting on the platen (41) according to pivoting axis (A3) parallel to the main axis and guided with respect to the platen on a plane orthogonal to the main axis and on which the tools are driven in rotation around respective rotation axes (A2) substantially parallel to the main axis, and the device including means for commanding the position of the levers for adjusting the radial positioning of the tools with respect to the main axis, the means for commanding the position of the levers including motor means (92) fixed to the chassis and means of mechanical transmission ensuring the link between said motor means and said levers (5), in such a way that the distance between the tools' axes and the main axis is continuously adjustable by commanding said motor means (92), said means of mechanical transmission including a set of bearings (7), mobile according to the direction of the main axis, the set of bearings including a first bearing (73) driven in axial translation by said motor means and a second bearing (74) linked in rotation with the rotary assembly (4) and in translation with the first bearing, the rotary assembly including means of mechanical linkage between the second bearing (74) and the levers (5) for transforming the axial translation movement of the second bearing into a radial movement of the tools' axes,
   characterised in that said means of mechanical linkage include, associated with each lever, a reversible screw-nut assembly (76, 77) linking the second bearing (74) to the lever (5) in such a way that an axial movement of the second bearing with respect to the platen causes the lever to pivot.
2. Device as per claim 1, characterised by the fact each tool (3) is mounted rotating on a first arm (51) of the lever (5) at a distance from its pivoting axis, and the reversible screw-nut system (76, 77) including, on its end connected to the lever (5), a stud (541) off-centre with respect to the axis of the screw-nut system and which engages in a groove (521) made at the end of a second arm (52) of the lever.
3. Device as per claim 2, characterised by the fact the stud (541) is mounted off-centre, in such a way it can adjust, by rotation of said stud around itself, the desired position of the corresponding lever (5) according to the angular position of the end of the screw-nut system that supports it.
4. Device as per claim 1, characterised by the fact the reversible screw-nut system (76, 77) includes, on its end connected to the lever, a pinion (58) engaging with a toothed quadrant (59) situated on the lever (5).
5. Device as per claim 1, characterised by the fact the nut (74) on the reversible screw nut system is fixed on the second bearing (74), and the screw (76) is rotating, guided in rotation on the platen (41), and its end is connected to the lever (5).
6. Device as per claim 1, characterised by the fact the rotary assembly (4) includes rotation linking means (44) linking the platen (41) and the second bearing (74) in rotation.
7. Device as per claim 6, characterised by the fact the rotation linking means include at least one pin (44) integral with the platen (41) and parallel with the main axis (A1) and sliding in a guide bushing (75) on the second bearing (74).
8. Device as per claim 1, characterised by the fact the rotary assembly (4) is driven in rotation by a motor (91) fixed to the chassis and connected to the rotating platen by a belt (911).
9. Device as per claim 1, characterised by the fact the motor means used to command the axial translation movement of the first bearing (73) include a motor (92) fixed to the chassis (1) and the first bearing is driven in axial translation by a tooth rack assembly (72) sliding in parallel with the main axis (A1) and meshing with pinions driven in rotation by said fixed motor (92).
10. Device as per claim 1, characterised by the fact the motor means used to command the axial translation movement of the first bearing include a motor (92) fixed to the chassis (1) and the first bearing is a toothed nut (85) including an internal thread engaged by screwing on to an axle-arm (12) of the chassis centred on the main axis, the toothed nut (85) meshing with a pinion (86) driven in rotation by said motor (92).
11. Device as per claim 1, characterised by the fact each tool (3) is driven in rotation on its support lever (5) by a set of pulleys and belts (51, 62) linking the tool (3) to a drive roller (61) held in rolling contact with a fixed internal crown (13) integral with the chassis (1).
12. Device as per claim 11, characterised by the fact the roller (61) is linked by a first belt (62) to an intermediate shaft (63) rotating in a bearing centred on the axis (A3) around which the tool support lever (5) pivots, and the intermediate shaft (63) is linked to the tool (3) by a second belt (64).
13. Device as per claim 11, characterised by the fact the roller (61) is mounted in rotation on a roller-carrier arm (6) mounted pivoting on the platen (41) as per axis (A3) around which the tool support lever (5) pivots, in such a way that the roller (61) is pressed against the internal crown (13).
14. Device as per claim 1, characterised by the fact it has a rotary crown (81) mounted in rotation on the chassis (1) and driven in rotation by a third motor (93) fixed on the chassis and an intermediate shaft (63') rotating in a bearing centred on the axis (A3) around which the tool support lever (5) pivots, and the intermediate shaft (63') is linked to the tool (3) by a set of pulleys and belts (83) and includes a toothed wheel (82) meshing with said rotary crown

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