Bar Feeder

Abstract

The device (1) for feeding bars (2) to a machine tool comprises a plurality of guide units (4) distributed circumferentially and extending parallel to a longitudinal axis (AL), each guide unit (4) reciprocable by a respective lever (5) and configured to be received inside and act on a respective bar (2). The device also comprises a support assembly (7) suitable for receiving and supporting the corresponding guide units (4) and the plurality of bars (2) adjacent to the drum (3), and a lifting device (8) movable from a lower position (P1) to an upper position (P2). The support assembly (7) and the bars (2) are lifted to the upper position (P2), and the feeding unit (GL) further comprises a selector unit (Gs) for selecting a single bar (2) at a time to achieve transfer of the bar to the respective guide unit (4) when the lifting device (8) is in the upper position (P2).

Description

[Technical Field]

[0001] The present invention relates to a device for feeding bars to a machine tool, in particular an automatic lathe. [Background technology]

[0002] Various devices are known for the automatic feeding of bars to the spindle of a lathe.

[0003] Generally, the bar feeder comprises a rotating drum rotatable about its horizontal longitudinal axis and supporting a number of guides suitable for receiving and guiding respective bars as they are fed to the lathe.

[0004] The bar feeder includes a loading mechanism for loading the bars, which includes a flat surface on which the bars are placed and a slide that is vertically movable and supports an articulated bracket that is lowered to remove one bar at a time and release the bar into a specific guide on a drum located below.

[0005] The articulating brackets are driven by suitable control members which move them from a holding position in which the lifted bars are prevented from falling, and a release position in which they are aligned with one another and thus define a chute for the same bars which can be discharged into said guide.

[0006] Guides are disposed longitudinally and circumferentially along the drum.

[0007] The guide can be opened by means of a rather complex mechanism comprising several articulated levers driven by suitable motors or cylinders housed in the lower zone of the device.

[0008] The bar feeder comprises a pushing device suitable for pushing the bar in the feed position, i.e. aligning it onto the machining zone of the spindle of the lathe.

[0009] The pusher device comprises a pusher block (post) which is advanced and retracted into the lathe by a screw-nut system driven by a conventional electric motor controlled by a suitable control unit.

[0010] The rather complex and delicate pusher device requires constant and thorough lubrication to avoid seizure or other undesirable damage phenomena. To check the correct movement of the pusher block, it is necessary to provide suitable position sensors located along the stroke of the pusher block, which further complicates an already complex pusher device.

[0011] In total, the known feeding devices mentioned above present different problems which are summarized below.

[0012] The first challenge is generally presented by the high structural and functional complexity of bar load mechanisms.

[0013] Furthermore, the screw-nut systems for driving the hold-down devices, together with the lubrication circuits required to ensure correct operation, are structurally complex, expensive and demanding from an operational and maintenance point of view.

[0014] A further problem is the structural and functional complexity of the mechanism with multiple articulated levers for opening the guides.

[0015] Finally, problems can arise with the guide units, which do not always guarantee correct advancement of the bar, and these bars often jam in the final section facing the lathe, especially in the case of bars with a significantly reduced diameter relative to the inner section of the guide units.

[0016] From DE 10 200 04 133 A1 an apparatus for feeding bars is known.

[0017] In light of the above, there is ample room for improvement in current bar feeders. [Prior art documents] [Patent documents]

[0018] [Patent Document 1] U.S. Patent No. 5,860,340 Summary of the Invention [Problem to be solved by the invention]

[0019] SUMMARY OF THE INVENTION It is an object of the present invention to improve upon current bar feeders.

[0020] Another object is to provide a feeding device that is simplified from a structural and functional point of view.

[0021] In particular, it is intended to propose a device in which the guide unit opening system is very simple, yet equally effective and reliable, and in which the operation of loading the bars and guide units is simplified.

[0022] A further object is to simplify the operation of pushing and advancing the bar inside the guide unit and reduce possible problems due to jamming, dynamic stresses and vibrations, friction and high temperatures that may occur during bar feeding.

[0023] It is also desirable to ensure proper operation of the drums and guides without necessarily relying on complex, expensive and redundant lubrication and cooling systems.

[0024] This can be achieved by an apparatus for feeding a bar to a machine tool as claimed in claim 1.

[0025] The present invention overcomes the above problems.

[0026] In particular, the device according to the present invention advantageously has a significantly simplified structural configuration with respect to prior art devices, resulting in, among other advantages, significantly reduced manufacturing costs, improved mechanical reliability, and significantly reduced undesirable vibrations.

[0027] Further features and advantages will become more apparent from the claims, the specification and the accompanying drawings.

[0028] The invention can be better understood and put into practice with reference to the accompanying drawings which illustrate embodiments thereof, by way of the following non-limiting examples, and in which: [Brief explanation of the drawings]

[0029] [Figure 1] 1 is a schematic front view of an apparatus according to the present invention; [Figure 2] FIG. 2 is a schematic perspective view of a portion of the device of FIG. 1. [Figure 3] FIG. 2 shows the rear of the device according to the invention. [Figure 4] FIG. 4 is an enlarged detailed view of a portion of FIG. 3. [Figure 5] 1 shows the opening lever mechanism of the device according to the invention in one operating position. [Figure 6] 5A and 5B show the opening lever mechanism of the device according to the invention in different operating positions. [Figure 7] 3A-3D show a series of operating positions that can be assumed by a loading unit included in a device according to the invention; [Figure 8] 3A-3D show a series of operating positions that can be assumed by a loading unit included in a device according to the invention; [Figure 9] 3A-3D show a series of operating positions that can be assumed by a loading unit included in a device according to the invention; [Figure 10] 3A-3D show a series of operating positions that can be assumed by a loading unit included in a device according to the invention; [Figure 11] 10 shows the adjustment possibilities in the loading unit and selector unit which are part of the device according to the invention; FIG. [Figure 12] FIG. 2 shows one operational configuration of a selector unit of a device according to the invention. [Figure 13]10 shows another operational configuration of the selector unit of the device according to the invention; FIG. [Figure 14] 1 shows one possible embodiment of the device according to the invention, corresponding to one spatial arrangement of the loading unit, the selector unit and the actuator elements for opening the guide units of the device according to the invention; [Figure 15] 10A and 10B show other possible embodiments of the device according to the invention, which correspond to other spatial arrangements of the actuator elements for opening the loading unit, the selector unit and the guide unit of the device according to the invention; [Figure 16] 1 shows the front of a device according to the invention intended to be placed adjacent to a lathe for machining bars; FIG. [Figure 17] 10 shows a reduction element mounted on an apparatus according to the invention and configured to slidably receive and guide a bar having a reduced diameter therein during feeding into a lathe; FIG. [Figure 18] 10 shows another reduction element mounted on an apparatus according to the invention and configured to slidably receive and guide a reduced diameter bar therein during feeding into a lathe; FIG. [Figure 19] FIG. 10 is a diagram showing a guide unit without a reduction element. [Figure 20] FIG. 10 is a diagram showing a guide unit with a reduction element. DETAILED DESCRIPTION OF THE INVENTION

[0030] With reference to the accompanying drawings, there is shown an apparatus 1 for automatically feeding a bar 2 into a machine tool, in particular a lathe of the single or multi-spindle type.

[0031] In particular, the device 1 has a first end EA adapted to be positioned adjacent the spindle of a lathe.

[0032] The device 1 comprises a rotating drum 3 rotatable about its own longitudinal axis AL and provided with a plurality of guide units 4 for the bars 2 arranged circumferentially and extending parallel to said longitudinal axis AL.

[0033] Each guide unit 4 consists of two parts 4A, 4B that can be reciprocated and opened and closed by a respective lever 5 located at one rear end (opposite the first end EA), and receives each bar 2 therein as it is advanced toward the machine tool.

[0034] Each openable guide comprises a fixed part, ie a part fitted in a stationary position on the drum 3, and a part which is movable transversely relative to the longitudinal axis AL of the drum 3.

[0035] The guide units 4 are maintained in a normally closed state by respective torsion springs 14 (shown in FIG. 4) which act on the movable parts by biasing them against the corresponding fixed parts.

[0036] By rotating the corresponding lever 5, this movable part is first removed from each fixed part and the bar 2 is inserted, and then, by the elastic return of the torsion spring 14, it approaches each fixed part and receives inside said bar 2, which must be guided during lathe processing.

[0037] The feeding device 1 comprises an actuator element 6 configured to operate each time by directly acting on a particular lever 5 in order to open the corresponding guide unit 4 .

[0038] As better shown in Figures 4 to 6, the actuator element 6 comprises a push-in stem 15 configured to press against a contact surface 17 of the respective lever 5 in order to push the corresponding guide unit 4 open.

[0039] A spherical element 16 suitable for bearing against an abutment surface 17 of the lever 5 is press-fitted into the outermost end of the push-in stem 15 .

[0040] Due to the particular geometry of the spherical element 16, the spherical element 16 adapts to the contact surface 17 whatever the position of the latter, ie whatever the orientation of the contact surface 17 during the rotation of the lever 5.

[0041] The push-in stem 15 is capable of linear movement. In particular, the actuator element 6 is a pneumatic cylinder and is therefore simple from a structural and functional point of view and is likewise reliable.

[0042] Due to the direct interaction, i.e. direct contact between the actuator element 6 and the lever 5, a significant structural and functional simplification of the opening system for opening the guide unit 4 is achieved, whereas in prior art systems all the tasks arising therefrom are rather complex.

[0043] The apparatus 1 comprises a support loading unit 7 suitable for receiving and supporting a plurality of bars 2 adjacent to the drum 3 .

[0044] The support loading unit 7 comprises a plurality of support bars 9 distributed along a longitudinally extending loading zone ZL adjacent to the drum 3. Each support bar 9 extends transversely to the aforementioned longitudinal axis AL. For example, as shown schematically in the figure, three support bars 9 may be provided, equally spaced apart and distributed along the loading zone ZL, although a different desired number and distribution of support bars 9 may be provided depending on the geometric and dimensional characteristics of the feeding device 1 or specific needs.

[0045] Obviously, the support bar 9 can be replaced by other equivalent elements of any desired shape, such as plates or the like.

[0046] Each support bar 9 is adjustably connected to a respective vertical upright 24. In particular, the support bars 9 are horizontally adjustable to adjust their distance from the drum 3, as better shown in Figures 11-13.

[0047] The position of each support bar 9 is manually or automatically adjustable by a respective drive member.

[0048] The device 1 is provided with a loading unit GL consisting of a lifting device 8 for the bar 2.

[0049] The lifting device 8 is movable from a lower position P1, better shown in FIGS. 7 and 10, to an upper position P2, better shown in FIG.

[0050] The lifting device 8 is configured to pick up one or more bars 2 from the support loading unit 7, lift the bars 2 to the upper position P2, and then deliver the bars 2 to the guide unit 4 in the open position, ready to receive the bars 2.

[0051] The lifting device 8 comprises a plurality of lifting bars 10 distributed along the loading zone ZL. Any suitable number and distribution of the lifting bars 10 can be provided, for example three. Obviously, the lifting bars 10 can be replaced by other equivalent elements of any desired shape, such as plates or the like.

[0052] Each lifting bar 10 extends transversely to the longitudinal axis AL and is inclined downwards so as to point towards the drum 3 .

[0053] The lifting device 8 comprises a plurality of lifting cylinders 11, for example hydraulic or pneumatic lifting cylinders 11, each configured to support and vertically move a respective lifting bar 10.

[0054] The lifting cylinders 11 are synchronized with one another.

[0055] The loading unit GL further comprises a selector unit GS suitable for cooperation with said lifting bar 10 .

[0056] In particular, the selector unit GS is configured to select only one bar 2 at a time when the lifting device 8 is in the upper position P2 so as to achieve transfer of the bar 2 to each guide section 4 arranged in the vicinity of the support input section 7.

[0057] The selector unit GS comprises a stationary plate 12 which projects vertically upwards and is connected to the end of the aforementioned support bar 9, i.e. the end closest to the drum 3. The stationary plate 12 is shaped to separate the bars 2 which are closer to the drum 3 than the remaining bars 2 resting on the lifting device 8.

[0058] The selector unit GS further comprises an abutment element 13 which cooperates with the stationary plate 12 and is suitable for receiving in an abutting manner and for guiding the bar 2 placed near the drum 3 towards the underlying guide unit 4 in an acceptable manner.

[0059] To be precise, the abutment element 13 comprises a tubular element that projects downwards in a substantially vertical manner. The position of the abutment element 13 is adjustable both horizontally and vertically.

[0060] The position of the abutment element 13 is manually or automatically adjustable by means of a respective drive unit.

[0061] For example, three abutment elements 13 distributed along the drum 3 or another desired number and distribution of abutment elements 13 can be provided.

[0062] The abutment elements 13 and the stationary plates 12 are arranged reciprocally to allow the selection of the bar 2 that has to be conveyed to the respective guide unit 4 .

[0063] During the transport of the bar 2, the bar 2 follows a downward path due to the downward movement of the lifting device 8.

[0064] The position of the support bars 9 is horizontally adjustable (as shown in Figures 12 and 13) to move the stationary plates 12 towards / away from the abutment elements 13 to accommodate the particular diameter of the bar 2 to be rested on. Each support bar 9 is thus fitted into a respective upright 24 by means of intervening connecting elements 25 which are releasable to adjust the horizontal position of the support bar 9.

[0065] 12 and 13 show two possible operating configurations, corresponding to two different diameters of the bar 2 (larger diameter) and the bar 2' (smaller diameter), respectively. As clearly shown, the reciprocal position between the abutment element 13 and the stationary plate 12 and drum 3 is adjustable to accommodate the various diameters of the bar 2 to be loaded.

[0066] In the embodiment of the device 1 shown in Figures 1 to 14, the support bar 9, the abutment element 13 and the actuator element 6 are positioned so that the bar 2 can be loaded at an angle into the guide unit 4 at the feed position W1 to the lathe.

[0067] According to the version of the device 1 shown in Figure 15, the actuator element 6', the support bar 9', the respective stationary plate 12' and the abutment element 13' are positioned so that the bar 2' can be loaded into the guide unit 4' which is in the bar pre-loading position W2 preceding the supply position W1.

[0068] This final configuration of the feeding device 1 allows the loading and feeding operation to be further accelerated. Indeed, it is not necessary to wait until the feeding of the current bar 2 to be machined into the lathe is completed so that the corresponding guide unit 4 located in the feed position W1 can be released in order to load a new bar 2. Instead, while the bar 2 to be machined is being fed into the lathe, it is possible to immediately continue loading the new bar 2 onto the adjacent guide unit 4 loaded in the pre-loading position W2. Once the processing of the current bar is finished, it is sufficient to rotate the drum 3 by an angle step and move the subsequent guide unit 4—already loaded previously—from the pre-loading position W2 to the feed position W1, thereby reducing the loading time by several seconds.

[0069] The actuator element 6 is fixed to a part of the frame near the end of the drum 3 where the lever 5 is located.

[0070] The fixing position of the actuator element 6 or 6' is selected depending on whether the actuator element 6 or 6' is required to open the guide unit 4 in the supply position W1 or in the pre-loading position W2 arranged at a higher position, taking into account the direction of rotation of the drum 3 shown in Figures 1, 14 and 14.

[0071] The device comprises a control and synchronization unit UC adapted to synchronously drive the actuator element 6 (or 6') and the loading unit GL.

[0072] In the device 1, a bar advancement device 18 is provided, which does not have a lubrication circuit and comprises a pusher 19 which is horizontally movable along a rail 31.

[0073] The pusher 19 is driven - via a chain or belt - by a friction wheel 20 which rotates by a flexible transmission element 21 , and by a brushless type motor 22 an encoder is connected for precise control of the position of said pusher 19 .

[0074] Because of this configuration, a brushless motor 22 and position encoder are incorporated, and the pusher 19 advancement system is accurate, free from issues such as seizure, and much simpler and easier to manage than conventional screw-nut advancement systems.

[0075] The device 18 is significantly simplified in structure and function compared to conventional screw-nut type complex systems, which require constant lubrication due to the special drive mechanism with a brushless motor, and are therefore expensive and demanding from both an operational and maintenance standpoint.

[0076] In order to correctly guide and feed the bars, especially those with small diameters, and to prevent the risk of jamming at the end of the guide unit 4 and at the end EA near the lathe, the feeding device 1 is in one embodiment provided with a sleeve 23, 23' or a reducing bushing.

[0077] A first type of reducing sleeve 23 is provided, made as a single tubular piece (as shown in Figure 17) and configured to be fixed to a respective tubular cylinder 30 extending to the front of the device 1 at the interface with the machine tool.

[0078] A second type of reducing sleeve 23' is provided, each consisting of a pair of fixed semi-tubular cylinders each connected by a screw 24 to one of the two parts 4A', 4B' that make up the guide unit.

[0079] Figure 19 shows a guide unit without a reduction sleeve 23', which accommodates a burr of a defined diameter, while Figure 20 shows a guide unit with a reduction sleeve 23 that optimizes the accommodation and guiding action for a burr 2' of a smaller diameter than in Figure 19.

[0080] The aforementioned reduction sleeves 23, 23' are made of a material with a low coefficient of friction and resistance to high temperatures, such as a material based on polytetrafluoroethylene reinforced with additives such as glass fibre and / or graphite and / or bronze (to give it high mechanical resistance).

[0081] Polytetrafluoroethylene (PTFE) is a semi-crystalline fluoropolymer with excellent thermal stability, chemical resistance, and a high melting point that operates from -200 to +260°C.

[0082] Among other characteristics, polytetrafluoroethylene has excellent sliding and non-stick properties, thus improving the operation of the guide unit 4 .

[0083] In one embodiment, the feeding device 1 further comprises a passive lubrication and cooling circuit that utilises the active lubrication and cooling circuit that a lathe or other machine tool would normally already have.

[0084] The passive lubrication and cooling circuit contained in the device 1 according to the invention comprises one or more ducts suitable for directing lubricating and cooling fluids into the guide unit 4 .

[0085] The passive lubrication cooling circuit is configured to be connected by a T-connection to the delivery branch of the active circuit that pumps the lubricant provided in the lathe.

[0086] The passive lubrication and cooling circuit comprises a collector for collecting the lubricant coming from the guide unit 4 and a return duct for returning the lubricant to the collecting and filtering tank of the machine tool.

[0087] Thanks to this feature, the correct operation of the drum 3 and guide unit 4 is ensured by a simple, cheap and effective solution, without having to resort to complex, costly and redundant dedicated lubrication and cooling systems.

[0088] With reference to Figures 8 to 10, the operation of the device 1 according to the invention will now be briefly disclosed.

[0089] In the rest position, corresponding to the lower position P1, the bar 2 rests on the support loading unit 7 and prevents the support plate 12 from falling (FIG. 7).

[0090] When the drum 3 needs to be loaded with a bar 2, the control and synchronization unit UC drives the actuator element 6 which opens the guide unit 4 which is in the loading position.

[0091] The control and synchronization unit UC further drives the loading unit GL, in particular the lifting device 8. More precisely, the various lifting cylinders 11 are driven to move the bar 2 from a lower position P1 to an upper position P2 by raising the bar 2 (FIG. 8).

[0092] In the upper position P2, the bar 2 is thus raised above the support loading unit and is at a higher height relative to the support plate 12.

[0093] On reaching the upper position P2, the bar 2 rolls along the inclined lifting bar 10, as shown in FIG. 8, and the bar 2'' closer to the drum 3 comes to rest directly on the abutment element 13.

[0094] All the bars then rest side by side and in contact with one another. Only the bar 2" located near the drum 3 rests directly on the abutment element 13, this bar 2" thus being positioned beyond the stationary plate 12. Essentially, the distance between the stationary plate 12 and the respective abutment element 13 is substantially equal to the diameter of the bar 2" to be loaded, the latter being positioned within the volume in which the stationary plate 12 and the abutment element 13 are located.

[0095] At this point, the lifting bar 10 is lowered again by taking the bar 2 into the lower position P1. In the lowering movement, the bar 2″ in the zone located between the stationary plate 12 and the abutment element 13 is guided to follow a path that leads to the inside of the corresponding guide unit 4.

[0096] During the lowering operation, the stationary plate 12 is inserted between the bar 2" to be loaded and the adjacent outer bar 2 intended to be returned to the supporting loading unit. In this way, the stationary plate 12 acts on the one hand as a guide for the bar 2" and on the other hand as a barrier for the remaining bars 2.

[0097] Once the bar 2 ″ has been introduced into the guide unit 4 , the stem 15 of the actuator element 6 can be retracted to call the lever 5 into the closed position of the guide unit 4 .

[0098] At this point, the pusher 19 is actuated to push the loaded bar 2 into the machine tool so that it can be machined.

[0099] From what has been disclosed above, it is clear that the feeding device 1 according to the invention makes it possible to achieve all the objects set out above. This device 1 is structurally and functionally simplified, has reduced weight and inertial mass, and is able to operate more quickly than devices of the prior art.

[0100] The overall slim and simple configuration overcomes the problems associated with lubricating and cooling the various components without the need to provide complex, costly and redundant lubrication and cooling systems.

[0101] The advancement of the bur 2 to be processed is optimized and free from vibrations, jamming, dynamic stresses and vibrations, which is particularly evident when reduction sleeves 23, 23' are used in the case of burs with reduced diameter.

[0102] The new system for opening the guide unit, which has an actuator element 6 acting directly on the lever 5, is extremely simplified, effective and reliable.

[0103] The new loading unit GL with selector unit GS significantly simplifies the operation of loading the bars 2 on the various guide units 4 .

[0104] The overall simplified configuration entails further reduced manufacturing and maintenance costs over prior art devices.

[0105] The device 1 can be configured and sized in any desired manner depending on the intended use and variations and / or additions to those disclosed and illustrated in the accompanying drawings.

Claims

1. A device (1) for feeding a bar (2) to a machine tool, said device (1) comprising: a rotating drum (3) provided with a plurality of guide units (4) arranged in the circumferential direction of the rotating drum (3) and extending parallel to a longitudinal axis (AL) of the rotating drum (3); Each guide unit (4) is made up of two parts (4A, 4B) that receive an individual bar (2) to be advanced by the machine tool therein and are reciprocally movable and openable / closable by a respective lever (5) disposed at one end of each guide unit (4); an actuator element (6) adapted to act directly on a particular lever (5) in each case in order to open the corresponding guide unit (4); a support assembly (7) comprising a plurality of support bars (9) adapted to receive and support the plurality of bars (2) as they are fed adjacent to said rotating drum (3); A loading unit (GL) the loading unit (GL) comprises a lifting device (8) movable and configured to pick up one or more bars (2) from said support assembly (7) and to lift said one or more bars (2) from a lower position (P1) to an upper position (P2), and further comprises a selector unit (GS) configured to select a single bar (2) when said lifting device (8) is in said upper position (P2) so as to achieve transfer of said bars to respective guide units (4) when said lifting device (8) moves downward; The selector unit (GS) has a stationary plate (12) protruding vertically upward and connected to the end of each support bar (9) of the support assembly (7) that is closer to the rotating drum (3), the stationary plate (12) being configured to separate the bars (2) that are closer to the rotating drum (3) from the remaining bars (2) that are resting on the lifting device (8).

2. 2. The apparatus of claim 1, wherein the support bars (9) of the plurality of support bars (9) are arranged along a longitudinally extending loading zone (ZL) adjacent to the rotating drum (3), and each support bar (9) extends transversely to the longitudinal axis (AL).

3. 3. The apparatus according to claim 2, wherein the lifting device (8) comprises a plurality of lifting bars (10) arranged along the loading zone (ZL), each of the lifting bars (10) extending transversely to the longitudinal axis (AL) and inclined downwards in the direction of the rotating drum (3).

4. 4. Apparatus according to claim 3, wherein the lifting device (8) comprises a plurality of lifting cylinders (11) drivable synchronously with one another and each suitable for supporting and vertically moving a respective lifting bar (10).

5. 5. The apparatus according to claim 1, wherein the selector unit (GS) comprises an abutment element (13) suitable for receiving, abutting and guiding the bars (2) located near the rotating drum (3), the abutment element (13) and the stationary plate (12) being arranged to be reciprocable to select the bars (2) and transport them to the respective guide units (4), the bars (2) being transported downwards along a path determined by the downward movement of the lifting device (8).

6. 6. The device according to claim 5, wherein the position of the support bar (9) is horizontally adjustable, manually or automatically, by a drive member, which moves the stationary plate (12) closer to or away from the abutment element (13) to accommodate the particular diameter of the bar (2) to be loaded.

7. 7. The device according to claim 5 or 6, wherein the position of the abutment element (13) relative to the stationary plate (12) and the rotating drum (3) is manually or automatically adjustable by respective drive units to adapt to the diameter of the bar (2) to be loaded.

8. 8. The device according to any one of claims 5 to 7, wherein the actuator element (6), the support bar (9) and the abutment element (13) are arranged so that the bar (2) can be loaded into the guide unit (4) at a feed position (W1) of the machine tool, or the actuator element (6'), the support bar (9'), the respective stationary plate (12') and the abutment element (13') are arranged so that the bar (2') can be loaded into the guide unit (4') at a preceding loading position (W2) of the bar preceding the feed position (W1).

9. 9. The device according to claim 8, wherein the actuator element (6) is fixed to a part of a frame near the end of the rotating drum (3) where the lever (5) is present, and the actuator element (6) is arranged to open the guide unit (4) in the feed position (W1) of the machine tool or to open the guide unit (4') in the pre-loading position (W2).

10. 10. The device according to any one of claims 1 to 9, wherein each guide unit (4) is maintained in a normally closed state by a respective torsion spring (14), and wherein the actuator element (6) comprises a pushing stem (15) configured to press against a contact surface (17) of a respective lever (5) so as to push the corresponding guide unit (4) open, the latter, and wherein at the outermost end of the pushing stem (15) a pressed-in spherical element (16) is formed to fit into any position of the contact surface (17) of the lever (5).

11. 11. Device according to claim 10, wherein said pusher stem (15) is linearly movable and said actuator element (6) is a pneumatic cylinder.

12. The device according to any one of the preceding claims, further comprising a control and synchronization unit (UC) configured to synchronously drive said actuator element (6) and said loading unit (GL).

13. 13. The apparatus of any one of claims 1 to 12, further comprising a bar advancement device (18) with a pusher (19) driven, via a chain or belt, by a friction wheel (20) rotated via a flexible transmission element (21) by a brushless motor (22) coupled with an encoder to control the position of the pusher (19).

14. 14. The device according to claim 1, further comprising a sleeve (23, 23') or a reducing bushing at the front end (EA) of the rotating drum (3), which is intended to come into contact with the machine tool, the sleeve (23, 23') or the reducing bushing being adapted to fit a bar (2') of reduced diameter, one part of the reducing sleeve (23) being made from a single tubular piece, the other part (23') consisting of a pair of tubular half-cylinders (23') fixed by a screw (24) to one of the two reciprocating parts (4A', 4B') that are arranged in the guide unit (4) and that make up the guide unit, the sleeve (23, 23') or the reducing bushing being made from a material based on polytetrafluoroethylene reinforced with the addition of glass fibre and / or graphite and / or bronze, which has a low coefficient of friction and is resistant to high temperatures.

15. 15. Apparatus according to any one of the preceding claims, further comprising a passive lubrication and cooling circuit with one or more ducts suitable for injecting lubricating and cooling fluid onto the guide unit (4), configured to be connected by a T-connection to a delivery branch of an active lubricant pumping circuit on which the machine tool is provided, a collector for collecting the lubricating and cooling fluid emerging from the guide unit (4), and a return duct for returning the lubricating and cooling fluid to a collecting and filtering tank on the machine tool.

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