The subject of the present invention is a work centre for machining parts in general.
 Work centres for machining parts made of wood are known which provide at least one head for machining the parts and which provide one or more support tables onto which the workpieces are locked. The machining head, which comprises a plurality of chucks carrying the machining tools, is movable along two axes of translation perpendicular to each other and about two axes of rotation; moreover, the work unit and each support table . are movable in relative motion along a third axis of translation perpendicular to the aforesaid two axes, of translation.
 These work centres operate according to a digitally controlled program and are capable of executing several operations on the part in a single step, or it is possible to produce profiles, milling, holes, tenons, mortices, etc.
 An important part of these work centres is constituted by the support tables which must fulfil conflicting requirements.
 In fact, the support tables must support the parts in a stable manner and at the same time must permit the head to move round the part for the machining: this means that the support tables must have an extent such as to contain the part as much as possible, but they must not be too bulky so as not to interfere with the machining head.
 It should also be stated that the workpieces have shapes and dimensions that are often very different from one another, and therefore the support table may be suitable for supporting some types of parts and not suitable for supporting other types of parts.  It is an aim of the present invention to propose a work centre in which it is possible to support and machine efficiently and completely one or more parts of various shapes and dimensions in a single machining step.
 Said aim is achieved by means of a ' work centre for machining parts in general, comprising at least one work unit equipped with means for machining the parts and further comprising support means for the parts, operatively associated with said work unit, wherein the work unit is movable along a first and a second axis of translation perpendicular to each other and about two axes of rotation, and wherein the work unit and the
support means are movable in relative motion along a third axis of translation perpendicular to the aforesaid two axes of translation, characterised in that said support means are movable along a fourth axis arranged parallel to a plane formed by the axes perpendicular to one another, and furthermore that said support means are movable along a fifth axis arranged orthogonally to the fourth axis.
 The invention will be understood more clearly from the following description of one of its exemplary embodiments, illustrated in the appended drawings, in which:
 Figure 1 shows in perspective view a work centre according to the invention;
 Figure 2 shows a perspective view of a detail of the work centre of Figure 1;
 Figure 3 shows, in a lateral perspective view, a part of the work centre of Figure 1 in a different operating position;
 Figure 4 shows a detail of the work centre of
Figure 1 together with two workpieces.
 As can be seen from the drawings, the work centre for machining parts, indicated generally by 10, comprises a portion 10A relative to the actual work unit and at least one portion 10B relative to the support
means for the workpieces (Figure 1) .
 The portion 10A comprises a support structure 11 along which an upright 12, or column, is slidable along a horizontal axis of translation X. On the upright 12 a saddle 13 or carriage is in its turn slidable along a vertical axis of translation Z. From the saddle 13 extends an arm 14 which rotates with respect to the saddle 13 about an axis of rotation as indicated by the double arrow A. • At the free end of the arm 14, for example a forked arm equipped with two prongs, a head 15 is mounted, carrying, for example, four chucks 16 arranged at 90° to one another, each of which is suitable for receiving a machining tool; the head 15 rotates with respect to the arm 14 about an axis of rotation as indicated by the double arrow B.  The portion 10B comprises at least one and preferably two guide benches or bases 17 along each of which at least one and preferably two respective carriages 18 slide.
 According to one embodiment, the guide base comprises a beam 21 arranged orthogonally to the plane formed by the first axis X and second axis Z. For example, said beam 21 has an I-shaped section, as can be seen from the dashed line in Figure 1. The upper surface of the I-beam and the flanks constitute fixing surfaces
for guides, for example of the type suitable for cooperating with pre-loaded roller or ball recirculation slide blocks, orientated according to axes Y1,Y2,Y3 and Y4 arranged orthogonally to a plane formed by the first axis X and second axis Z of translation of the work unit. The lateral re-entrants of the I-beam are also suitable for receiving transmission devices 22 (indicated by a dashed line in Figure 1) . Provided at the base of the I-beam 21 are a plurality of feet 23 for support at a base, for example of the self-levelling type. The beam is covered at the ends by a sheet metal wall and laterally by conventional protective members suitable for preventing chips or dirt from reaching and soiling the transmission devices and the guides.  Connected operatively and slidably to the guides of the base or bases 17, at least one and preferably four carriages 18 are provided.
 According to one embodiment, said carriages comprise a bracket body coupled by means of slide blocks -to the guides of the base arranged above and at the side of said I-beam. In particular, each carriage 18 comprises an upper plate 24 which is cantilevered laterally to the guide base 17 forming a fixing plane for fixing guides 25 arranged orthogonally to the axis Yl, Y2, Y3 and Y4 defined by the guides of the base 17.
Said guides 25 of each carriage 18 define a fourth axis XI, X2, X3, and X4. According to a particular embodiment, said carriage guides 25 are of the type suitable for co-operating with preloaded slide blocks for example with recirculation of balls or rollers (Figures 2 and 3) . The cantilevered part of the body of said carriages is reinforced by means of gussets 26. Operatively connected to each carriage is one end of a cable-carrying chain 30, fixed at the other end to the base and suitable for supporting the supply cables for the devices transported by the carriage (Figure 2) .  To the guides of each carriage there is operatively connected so as to be selectively slidable at least one cross-member 27 arranged partially cantilevered from the carriage 18 in the direction of the work unit 15. According to one embodiment, at least half of the cross-member 27 'is cantilevered towards the work unit (Figure 3) . By selectively slidable operative connection there is to be understood a slidable connection between slide blocks, for example slide blocks, rigidly connected to the cross-member, of the pre-loaded, ball recirculation type, and the bracket guides 25, with which there is associated a device for removable locking of the cross-member in a specific position, for example, a position established by means
of a rule associated with the carriage and arranged parallel -to the bracket guides- 25, and also, alternatively, a linear position transducer also suitable for connection to a conventional device for actuation of the cross-member with feedback. Each cross-member has at the top a surface suitable for the fixing of guides 28 arranged transversely to the fourth axis XI, X2, X3 and X4 and parallel to the third axis Yl, Y2, Y3 and Y4, and also orthogonally to the plane formed by the first and second axis X, Z. Said cross- member guides 28 define a fifth axis Y1',Y2',Y3' and Y4* .
 ' Operatively connected to the cross-member guides 28 in a selectively slidable manner are at least one, preferably two column support members 29. Also in this case, by selectively slidable operative connection there is to be understood a slidable connection between slide blocks, for example slide blocks, rigidly connected to the column support member, of the pre-loaded, ball recirculation type, and the cross-member guides 28, with which there is associated a device for removable locking of the column support member in a specific position of the guides, for example a position established by means of a rule associated with the cross-member and arranged parallel to the cross-member guides 28, and also,
alternatively, a linear position transducer also suitable for connection to a conventional device for actuation with feedback of the column support member.  Each of said column support members 29 has at the top a support table 19 for a workpiece 32. Each column support member has a height "h" from the cross-member 27 such as to permit the work unit, and in particular the head 15, and even more particularly the tool, to machine the part 32 on its portions facing towards the cross- member 27 (Figure 4) . In other words, the height of each column support member is such as to permit the head or part of it or the tool to be arranged laterally and preferably below the workpiece.
 According to one embodiment, each of the column support members 29 comprises at the free end, or the opposite end from the cross-member 27, a support plate 20. Said support plate is preferably partially cantilevered from the column support member, so as to facilitate further the approach of the head 15 to the workpiece 32. In particular, at least one edge of said support plate 20 comprises a groove 33 suitable for the connection in a defined position of a fixing member 34 for fixing the workpiece to the support plate, such as, for example, a mechanical, hydraulic or pneumatic clamp. According to a further embodiment, the support table 19
and/or the support plate 20 comprises a plurality of holes 35 operatively connected to suction devices so as to create suction suitable for holding the workpiece on the table/plate itself.
 The work centre 10 comprises a series of motors which serve to move the above components along the first, second and third axis X, Yl,Y2, Y3, Y4 and Z and on the axes of rotation according to the double arrows A,B, and which serve to rotate the chucks.
 According to a particular embodiment, the work centre further comprises a further series of motors which serve to move the at least one cross-member 27 and the at least one column workpiece support member 29 along said fourth and fifth axis Xl,X2,X3,X4, l ' , Y2 ' , Y3 ' and Y ' . Alternatively, the sliding of the cross-member along said fourth axis and of the column support member along said fifth axis may be effected by means of actuators or manually and devices are provided which serve to lock the cross-member and the column member in any position of the travel along its sliding axis.  All or some of the aforesaid motors are actuated by a suitable electronic operating and control unit which operates according to digitally controlled programs .  As stated above, the upper surface of the support
tables and of the support plate is drilled (for the sake of simplicity, the holes are not illustrated in all the drawings) and the holes are connected to suction devices, so as to create suction on the support table to hold the workpiece on the table itself.' Said support tables 19 and 20 may be equipped with suitable workpiece locking members 34, as an alternative to, or in addition to, locking by means of suction.
 The operation of the work centre 10 is as follows .
 The workpiece or workpieces are loaded onto one or more of the support tables 19 and 20 relative to one of the four carriages 18 and are suitably locked on said support tables .
 The carriage 18 with the parts is advanced, depending on the carriage, along the axis Yl, Y2, Y3 or Y4 towards the portion 10A of the work centre 10 relative to the work unit. Similarly, the machining head 15 is moved along the axes X and Z to bring it level with the workpiece or workpieces.
 For machining, as is known, the arm 14 rotates in the direction of the double arrow A and the head 15 in the direction of the arrow B, respectively to select the machining direction (front/from top/from bottom, lateral, oblique) and the tool required. Then, by
moving the machining head 15 according to" a predetermined digitally controlled program along the axes X, Z, and also A, ' B and optionally the carriage 18 along the axis Yl, Y2, Y3 or Y2, depending on the carriage, the required machining is carried out.  During this machining of the parts, the support tables 19 and 20 carried by the other carriages 18 can be loaded with new workpieces. When machining is completed, the first carriage 18 is returned and a second carriage 18 is advanced, bringing the head 15 level with it to machine the new workpieces .  The parts already machined, on the support tables 19 and 20 of the first carriage 18, can be discharged and said support tables are ready to be loaded with new workpieces .
 Then by moving the four carriages 18 alternatively, successive machining of new parts is carried out.
 Owing to the support means 19 and 20 and their possibility of moving along said third, fourth and fifth axis, it is possible to support and machine efficiently and completely one or more parts of various shapes and dimensions in a single machining step, fulfilling the conflicting requirements mentioned in the introduction.  A single part of large dimensions may also be
locked onto several . support means, a good support surface also being available in this case.  Moreover, owing to the provision of column support members, the head can move close to the part, making it possible to execute multiple machining operations in a single placement.
 Also particularly advantageous is the fact that providing cantilevered carriages, and cross-members, also cantilevered, movable on the carriages, further increases the mobility of the head round the part while maintaining optimum support and clamping of the part. In other words, a very large work volume for the head is obtained with respect to that of machines having a first axis X and a second axis Z of equal extent, and moreover this work volume extends further round the part, permitting machining also on previously inaccessible faces of the part.
 It is clear that further variants and/or additions to what has been described and illustrated may be provided.
 . In particular, the structure of the portion of the work centre relative to the work unit for the parts may have a structure different from that illustrated.  With regard to the portion relative to the support means for the parts, said support means may have
shapes and dimensional ratios different from those illustrated; the shapes' and dimensional ratiosillustrated, however, prove to be functionally very advantageous. Moreover, there may be more than four support means. In a simplified version, it is possible to provide a single carriage with support tables; the double and quadruple carriage, however, prove to be functionally very advantageous . The means for regulating the position of the carriages, the cross- member and the column members along said third, fourth and fifth, axis may be of any type. ' Other relative movements may be provided between the column members.  The work head may also be provided with a further movement along an axis perpendicular to the axes X, Z and therefore parallel to the axes Y1,Y2,Y3 and Y4.  The work centre according to the present' invention may be advantageously used for the machining of wooden parts, for example for the production of furniture. However, its use for the machining of parts made of other material, for example of plastics material, cannot be excluded. k -k k ~ k -k k