"MOVABLE TABLE ASSEMBLY FOR A MACHINE TOOL OF LARGE

DIMENSIONS"

[0001]The present invention belongs to the field of machine tools; in particular, the present invention relates to a movable table assembly for a machine tool of large dimensions, such as a milling machine or a gantry boring machine.

[0002]Such machines are usually intended for mechanical processing operations on very bulky and heavy semi finished products, such as reactor casings for the chemical or nuclear industry, ship masts, and the like. For this reason, even if the dimensions of the machines themselves are considerable (for example, the Applicant manufactures and markets the gantry milling machine referred to as ATLAS, provided with a bench up to 30 meters long), it is highly important to limit the dimensions of some accessory assemblies, so that they do not interfere with the movement operations of the semi- finished products to be processed or with the processing operations themselves.

[0003]It is the object of the present invention to provide a movable table assembly for a machine tool of large dimensions, such as a milling machine, a lathe, or a gantry boring machine, for which the overall dimensions of the motor assembly, intended for rotationally driving the table, are highly small, while maintaining the performance unchanged.

[0004]Such an object is achieved by a table assembly according to claim 1. The dependent claims identify further advantageous embodiments of the table assembly. [0005]The features and advantages of the table assembly according to the present invention will become apparent from the following description, given by way of non- limiting example, in accordance with the accompanying drawings, in which:

[0006]- figure 1 shows a machine tool according to an embodiment of the present invention;

[0007]- figure 2 depicts a table assembly (without table) according to an embodiment of the present invention, supported by benches;

[0008]- figure 3 depicts a sectional view of a table assembly according to an embodiment of the present invention, supported by benches; [0009]- figure 4 is an enlargement of a detail of figure 3 which highlights a rotation assembly of the table assembly.

[0010]For clarity of presentation, reference will be made hereinafter to a gantry milling machine; however, the invention is feasible on any other machine tool of large dimensions, for example a boring machine or a lathe.

[0011]In the figures of the accompanying drawings, 1 indicates a machine tool of large dimensions as a whole, for example a gantry milling machine, resting on a ground plane G. The machine tool 1 comprises, for example, a gantry structure 2 comprising a pair of vertical uprights 4 and a crosspiece 6 supported by said uprights 4; the pair of uprights 4 and the crosspiece 6 delimit an opening 7 of the gantry structure 2. [0012]The crosspiece 6 is translatable on command along said uprights 4, along a vertical axis W. The machine tool 1 further comprises a cart 8, supported by the crosspiece 4, which is translatable on command along the crosspiece 4, along a transverse axis Y. The machine tool 1 finally comprises a ram (not shown), supported by the cart 8, which is translatable along a further vertical axis Z, carrying a rotating spindle, to which a tool can be applied in order to perform chip removal processing operations. [0013]The machine tool 1 further comprises a support apparatus 10, constrained to the ground plane G, having an extension along a longitudinal direction X, for example such as to cross the opening 7 of the gantry structure 2. [0014]In the example shown, the uprights 4 are fixed i.e., they are constrained to the ground plane G; according to a further embodiment, the uprights are movable on command parallel to the longitudinal direction

X. [0015]The support apparatus 10 comprises a pair of benches

12, each of which extends mainly along the longitudinal axis X and is transversely spaced apart from the other, and at least one table assembly 14 for supporting the semi-finished product to be processed. [0016]An embodiment of such a support apparatus is shown in Italian patent no. 1413392 to the Applicant, the teaching of which on the construction of such an apparatus is explicitly incorporated herein.

[0017]According to an embodiment, the machine tool 1 comprises two table assemblies 14, one arranged on one side and the other on the other side of the gantry structure 2.

[0018]The table assembly 14 comprises a slide 16 supported by the benches 12 and which is translatable on command along said benches 12, along a longitudinal axis X, and a table 18 supported by the slide 16 and which is rotatable with respect to a vertical axis C.

[0019]The table assembly 14 further comprises slide translation means adapted to be driven to translate the slide 16 along said benches 12. [0020]According to a preferred embodiment, the slide translation means comprise at least one gearmotor assembly 20 on board the slide 16, engaged with a rack 22 fixed to the respective bench 12. [0021]For example, the gearmotor assembly 20 is arranged between the two benches 12 and comprises a motor 24, having a motor axis 26 orthogonal to the longitudinal axis X and to the vertical axis C, and a reduction gear 28 having an inlet, engaged with the motor 24, and an outlet, engaged with the rack 22, coaxial to the motor axis 26.

[0022]Preferably, the slide translation means comprise at least two gearmotor assemblies 20, for example arranged on the same side of the slide 16. Said gearmotor assemblies 20 are arranged so that the respective motors 24 are transversely spaced.

[0023]Preferably, the slide translation means comprise two pairs of gearmotor assemblies 20, each pair being arranged on one side of the slide 16, so that the motors are driven in opposition, to eliminate the clearances between the outlet pinion of the respective gearmotor and the rack (Twin-Drive).

[0024]The table assembly 14 further comprises table rotation means adapted to be driven to rotate the table 16 about the vertical axis C. [0025]The table rotation means comprise at least one rotation assembly 30 on board the slide 16, engaged with a ring gear 32 of the table 18.

[0026]The rotation assembly 30 comprises a torque motor 34 having a vertical motor axis 36, i.e., parallel to the vertical axis C, and a reduction gear 38, preferably epicyclic, having an inlet, engaged with the torque motor 34, and an outlet pinion 40, engaged with the ring gear 32 of the table 18, coaxial to the motor axis 36. [0027]In particular, the epicyclic reduction gear comprises a sun gear, planetary gears, a planetary carrier, and a ring gear for reduction gear; the sun gear is rotatable and engaged with the motor axis 36 of the torque motor 34, the ring gear for reduction gear is fixed, the planetary gears roll on the sun gear and on the ring gear for reduction gear, and the planetary carrier is engaged with the outlet pinion 40.

[0028]Preferably, the outlet pinion 40 meshes directly with the ring gear 32 of the table 18; according to an alternative embodiment, at least one idle gear is placed between the outlet pinion 40 and the ring gear 32.

[0029]Preferably, the rotation assembly 30 is arranged between the two benches 12; for example, the rotation assembly 30 is arranged between two gearmotor assemblies 20 of the slide translation means. [0030]Preferably, the table rotation means comprise at least two rotation assemblies 30, each rotation assembly 30 being arranged on a side of the slide 16. In this variant, when the table 18 must provide a continuous rotation, generally at high speed, for performing turning or boring operations, the two torque motors are driven in concert; on the other hand, when the table 18 must provide a positioning rotation, for example in milling operations, the two torque motors are driven in opposition, to eliminate the clearances between the outlet pinion of the respective reduction gear and the ring gear of the table (Twin-Drive).

[0031]Innovatively, the table assembly according to the present invention meets the needs of the field, since it allows to minimize the overall dimensions of the motors required for the rotation of the table.

[0032]In particular, according to an advantageous aspect, the combination of the torque motor and the reduction gear allows to exploit the compact dimensions of the torque motor and the high speeds which can be reached with the reduction gear.

[0033]It is apparent that, in order to meet contingent needs, those skilled in the art may make changes to the table assembly described above, all contained within the scope of protection as defined by the following claims.