WO2022263380A1

WO2022263380A1 - Bar feeder for feeding tool machines with optimized bar change cycle

Info

Publication number: WO2022263380A1
Application number: PCT/EP2022/066033
Authority: WO
Inventors: Giovanni Pietro Maria LASI
Original assignee: Lasi Giovanni Pietro Maria
Priority date: 2021-06-17
Filing date: 2022-06-13
Publication date: 2022-12-22
Also published as: TW202306669A; IT202100015848A1

Abstract

Bar feeder (1) for feeding a tool machine with optimized bar change cycle, comprising: a guide channel, provided with a fixed portion and a movable portion, arranged to receive a bar; a bar pusher, provided at the front with a gripper to constrain the bar and movable within said guide channel to push the bar into a working position at least partially extracted from the bar feeder; and clamping means (17) adapted to lock the longitudinal sliding of the bar to allow the engagement of the new bar to be machined on the gripper of the bar pusher and the disengagement of the residual piece (13) at the end of the machining; wherein said clamping means (17) are configured to act on the residual piece (13) when the movable portion (10) is in the open position.

Description

Title: Bar feeder for feeding tool machines with optimized bar change cycle

DESCRIPTION

Field of Application

In its most general aspect, the present invention refers to a bar feeder for feeding tool machines and in particular automatic lathes.

The technical field of the invention relates therefore to tool machines, in particular lathes, and can be usefully applied in all the manufacturing fields in which it is employed.

Prior art Bar feeders are automatic devices arranged to progressively feed a tool machine, generally a lathe, with bars of different diameters to be machined by material removal; at the end of the cycle of bar machining, the feeder retracts the residual piece from the tool machine and expels it before loading the next bar. The currently used bar feeders consist: of a guide channel, usually consisting of a series of pairs of half-shells, wherein the upper ones thereof can be opened by means of designated actuators to allow the introduction of the new bar to be machined; of a pusher, commonly called bar pusher, provided with a gripper which inserts itself in the rear end of the bar to allow it to be moved and the residual piece to be extracted at the end of machining; of a drive connected both to the bar pusher and to a further auxiliary carriage to manage to move both of them in the various steps of the machining cycle; and of a clamping device for the extraction and the expulsion of the non-machinable residual piece and the subsequent introduction of the new bar in the gripper of the bar pusher.

During the bar change cycle, in which the residual piece is extracted and expelled and a new bar to be machined is introduced, the bar pusher has to reach the completely backward position; at this time, it is extracted from the lower part of the guide channel after the piece has been expelled. The extraction of the bar pusher clears the space required for the introduction of the new bar into the guide channel, said bar being subsequently advanced by the action of the auxiliary carriage in the so- called pre-advancement step which allows to pre-introduce the bar in the hollow spindle of the tool machine, thus bringing the bar in the position immediately in front of the gripper of the bar pusher. In the next step, the auxiliary pre-advancement carriage returns in the starting, completely backward, position and subsequently the guide channel can be closed again by bringing the bar pusher again aligned with the bar, which is clamped by suitable means and inserted in the gripper of the bar pusher. In the next steps, said clamping means open, thereby freeing the bar and allowing it to advance to a working position after it has been pushed by the bar pusher, thus concluding the so-called bar change cycle.

The temporal sequence of all the steps of the bar change cycle, as they are described above, determines a total time hereafter identified as “bar change time”. In other words, the bar change time is a lapse of time between the end of machining a bar and the beginning of machining the next bar.

In traditional feeders, the bar change time is represented by the sum of the times required for the different steps previously described, as can be observed in the time chart of Figure 11.

Usually, the time of bar change cycle is about 20 and 30 seconds for bars long about 3 meters and increases with an increasing length of the bar and of the bar pusher. In particular, the steps of extraction of the residual piece, of pre-advancement of the new bar to be machined and of return of the pre-advancement in the backward position constitute an important part of the total time of bar change cycle, especially in the case of long bar pushers, which are increasingly widespread due to the longer length of the spindles used in modern tool machines with numerical control. The value of the bar change time is an important performance indicator of bar feeders since it is to all intents and purposes a downtime for the machining of the machine to which the feeder is slaved. Trying to reduce as much as possible said time is therefore fundamental to increase productivity and efficiency of the total machining cycle, especially in those machining wherein bar change is frequent (for example for simple, short-duration machining on long pieces, wherein bars wear rapidly out) .

The solutions used so far to try to reduce the above-mentioned bar change time are mainly directed to speed up the single steps thereof, for example by increasing the speed of translation of the bar pusher and of the auxiliary carriage for the pre-advancement of the bar, or of the movements of the mechanisms in the other steps.

Although effective, the above-mentioned expedients reduce only marginally the total time, and are not able to significantly decrease it.

A bar feeder according to the prior art is disclosed for example in the prior document EP 1 338 362, corresponding to the preamble of claim 1.

The technical problem underlying the present invention is thus to devise a bar feeder for feeding tool machines which, using innovative, but still simple and reliable solutions, allows to significantly reduce the time of bar change cycle obviating the above-mentioned issues of known feeders.

Summary of the invention

The technical problem identified above is solved by a bar feeder for feeding a tool machine, comprising: a guide channel arranged to receive a bar to be fed to a tool machine, said guide channel comprising a fixed portion and a movable portion which is movable between a closed position, next to the fixed portion and an open position away from the fixed portion; a bar pusher, provided at the front with a gripper to constrain the bar and movable within said guide channel to push the bar in a partially extracted working position with respect to the bar feeder; a main drive for longitudinally moving said bar pusher along said guide channel; and clamping means adapted to lock the longitudinal sliding of the bar to allow the engagement of the new bar to be machined on the gripper of the bar pusher and the disengagement of the residual piece at the end of the machining; wherein said bar pusher is slidingly constrained to said movable portion of the guide channel and said clamping means are configured to act on the residual piece engaged in said bar pusher housed in the movable portion when said movable portion is in the open position.

Thanks to the above-described solution, it is therefore possible to at least partially overlap some steps of the bar change cycle. In particular, the step of introduction of the new bar and the subsequent step of pre advancement of the same bar can be conveniently performed simultaneously with the steps of return of the bar pusher after machining and of extraction i.e., expulsion of the residual piece.

In fact, the suggested configuration allows to all intents and purposes to use the open movable portion of the guide channel as a return path for the bar pusher with residual piece, said return path being separated and not interfering with the area of introduction of the bar defined by the fixed portion of the guide channel.

In a preferred embodiment, said clamping means are integral with the movable portion of the guide channel in its relative motion with respect to the fixed portion; in other words, they are directly supported on the movable portion and, when the latter is open, they act on the auxiliary bar path defined by the latter.

Alternatively, the clamping means can be split in two i.e., can comprise two fixed devices: a first clamp acting at the fixed portion to lock the bar upon engagement on the gripper and a second clamp acting at the movable portion lo lock the residual piece upon release from the gripper.

Preferably, guide supports are arranged to hold the bar pusher at the bottom when the movable portion is in the open position. Said guide supports can divide into first guide supports arranged at the front with respect to the clamping means and second guide supports arranged at the rear with respect to the clamping means, said first guide supports being retractable independently from said second guide supports.

In this case, the first guide supports can be retracted during the bar change cycle, during a step of closing the movable portion of the guide channel, to avoid interferences with the bar already introduced into the fixed portion.

On the contrary, the second guide supports, which have to accompany the bar pusher into the backward position at the time of closure, are preferably kept always in the extracted configuration, being retracted only when change or maintenance of the bar pusher are needed.

Preferably, said guide supports can be mounted on a longitudinal member, said guide supports being retractable thanks to a cam mechanism that defines a transversal movement of the longitudinal member. Said cam mechanism kinetically connects the movements of the guide supports to the movements of opening and closure of the movable portion of the guide channel.

Preferably, each guide support has different faces with alternative profiles intended for different diameters and/or configurations of different bar pushers and may be alternatively mounted with a different face facing towards the bar pusher.

Preferably, the main drive is integral with the movable portion of the guide channel in its relative motion with respect to the fixed portion.

The bar feeder according to the present invention can also comprise a pre-advancement device arranged to bring the bar from an initial position thereof of introduction into the fixed portion of the guide channel into an advanced position thereof with respect to a start-stroke position of the bar pusher, said pre-advancement device being driven by a secondary actuator that is independent with respect to the main drive.

In this way, the pre-advancement device can be independently moved, and, in particular, said device can be brought to the rear end-stroke position, while the bar pusher acts on the bar, thereby feeding it to the tool machine.

In particular, said pre-advancement device can comprise a pre advancement carriage arranged to push the bar along the fixed portion of the guide channel, said pre-advancement carriage being movable between a centered position, in which the pre-advancement carriage is aligned with the fixed portion of the guide channel and is operational on said bar, and an eccentric position, in which the carriage is offset with respect to the guide channel. In this case, the pre-advancement carriage moves to the centered position when said movable portion of the guide channel is in the open position, and to the eccentric position when said movable portion of the guide channel is in the closed position, said eccentric position allowing, as mentioned above, a return of the pre advancement carriage from a front end-stroke position to a rear end- stroke position, without interfering with the bar pusher when the movable portion is in the closed position on said fixed portion of the guide channel.

The previously identified technical problem is also solved by a method of operation of a bar feeder comprising the steps of: introducing a bar into a fixed portion of a guide channel of a bar feeder; bringing a movable portion of the guide channel into a closed position above said fixed portion of the guide channel; locking the longitudinal stroke of the bar through clamping means; advancing a bar pusher along the guide channel, so as to engage said bar on a front gripper of the bar pusher; pushing, by means of the bar pusher, said bar into a working position on a tool machine at least partially extracted from the bar feeder; once the machining of the bar has been completed, bringing said bar pusher back, with the residual piece still engaged on the gripper, along said movable portion of the guide channel until a backward position has been reached; once said backward position of the bar pusher has been reached, locking said residual piece through said clamping means and bringing the bar pusher back along said movable portion up to a further backward position, thus freeing the residual piece from the gripper; wherein at least said step of locking said residual piece and of bringing the bar pusher back until the further backward position has been reached are made with the movable portion of the guide channel at least partially open, thus keeping the fixed portion of the guide channel free for the possible introduction of a new bar. Preferably, the new bar is introduced during the step of bringing the bar pusher back; said new bar is then advanced to a start-stroke position through a pre-advancement device during the expulsion of the residual piece.

Further characteristics and advantages of the present invention will become apparent from the following description of a preferred illustrative embodiment, given by way of a non-limiting example, with reference to the attached drawings.

Brief Description of the Drawings

Figure 1 shows an overall perspective view of a bar feeder according to the present invention, seen from the side of the bar store with the guide channel in the closed configuration;

Figure 2 shows an overall perspective view of the bar feeder, seen from the side opposite the bar store with the guide channel in the closed position; Figure 3 shows an overall perspective view of the bar feeder, seen from the side of the bar store with the guide channel in the open position, the graphical representation of the bar store being omitted for greater clarity;

Figure 4 shows a perspective view of the bar feeder in a first step of the bar change cycle, consisting of the backward movement the bar pusher and of the concurrent opening of the guide channel, with the new bar to be machined falling into said guide channel;

Figure 5 shows a detail of the engagement of the bar pusher into an upper half-shell which constitutes the guide channel of the bar pusher;

Figure 5A shows a perspective view of the feeder in the second step of the bar change cycle consisting of the pre-advancement of the bar and of the concurrent extraction and expulsion of the residual piece;

Figure 6 shows a perspective view of the bar feeder during a step of the bar change cycle which involves closing the guide channel, the subsequent introduction of the bar into the gripper of the pusher and the return of the pre-advancement carriage of the bar, in said view being omitted some sectors of the upper half-shell for clarity of exposition;

Figures 7 and 7A show sectional views of the bar feeder in the two positions, respectively with the guide channel being closed, i.e., with the device of pre-advancement of the bar in eccentric position, and with the guide channel being open, i.e., with the pre-advancement device aligned with the channel;

Figures 8, 8A, 9 and 9A show perspective views of construction details of the devices for moving the retractable guide supports which support the bar pusher in the steps in which the guide channel is not closed;

Figure 10 shows a perspective view of a longitudinal member for supporting the retractable guide supports of the bar pusher, on which different possible conformations for said retractable guide supports are shown;

Figure 10A shows a perspective view of means for clamping the residual piece of the bar which are used in the bar feeder, in exploded configuration;

Figure 10B shows the means for clamping the residual piece of the bar of Figure 10A in assembled configuration;

Figure 11 shows a time chart with the steps of the bar change cycle in bar feeders according to the prior art;

Figure 12 shows a time chart with the steps of the bar change cycle in bar feeder according to the present invention.

Detailed description

With reference to the attached drawings, 1 generically refers to a bar feeder for feeding tool machines.

The position references used in the present description, comprising indications such as lower or upper, under or above, or similar expressions, are always referred to the illustrative configuration shown in Figure 1, and, in any case, they should not be construed as limiting. Further in the description, the portion of the machine which faces the tool machine for feeding the bars is considered the “front” portion, and the opposite part of the machine is the “rear” one; in other words, the bar which is fed is moved from the rear part towards the front part of the bar feeder.

The bar feeder comprises a beam 2, shown by way of example as a rectangular-shaped section bar, which extends for the whole length of said feeder.

Said beam 2 has a supporting function, and a plurality of uprights 3 for supporting a sloped plane, on which a bar store 4 is made, are secured to said beam by suitable fixing means.

Also secured to the beam 2 are a plurality of lower half-shells defining the lower part, i.e., a fixed portion 5, of a guide channel 6; and moreover a plurality of lower supports 7 inside which a shaft 8 is rotatably housed, on said shaft being integrally mounted upper supports 9 of the upper half- shells, which can be opened and define the upper part, i.e., a movable portion 10, of the guide channel 6. The shaft 8 is suitably driven by an opening and closing actuator 11, for example a hydraulic or pneumatic cylinder.

Also secured to the beam 2 is a chute 12, which is arranged for the expulsion of a residual piece 13 of a bar at the end of the lathe machining.

Finally, the beam 2 supports a device of pre-advancement of the bar 14, described in greater detail below.

Front closing plates and/or housings, not shown in the attached drawings for obvious purposes of clarity of depiction and exposition, may also be provided in a per se known manner.

The above-mentioned upper supports 9, besides supporting the upper half-shells, support also different auxiliary devices which therefore move with them. Said auxiliary devices comprise: a main drive 15, arranged to move a bar pusher 16 of a per se known conformation; a clamping device 17, constituting clamping means arranged to expel the residual piece 13 and to introduce a new bar 18 to be machined in a gripper 19 of the bar pusher 16; and retractable supports 20, 21 of the bar pusher.

At the bar store 4, selection devices 22, per se known, are provided, which allow to select the new bar 18 to be machined from the bar store 4 to introduce it into the fixed portion 5 of the guide channel 6.

The guide channel 6 of the bar feeder may be of the traditional type, such as the one shown in the mentioned drawings, i.e., consisting of a plurality of lower half-shells, which constitute the fixed portion 5 and are secured to the beam 2 directly or by interposition of designated supports 23, whereas the upper half- shells, which constitute the movable portion 10, are structured so that they can be moved apart from the lower ones 6 by rotation, translation or roto-translation to allow the introduction of a bar 18 into the guide channel 6. After the introduction of the bar 18, the movable portion 10 can be brought near again to close the guide channel 6, so as to guide the bar pusher 16 with the new bar 18 during the subsequent steps of advancement and machining in the tool machine.

As an alternative to what is described above, said guide channel 6 can consist of a series of bushings or supports or rollers of different shapes and which are suitably shaped, as it also results from other executions which are here not shown since they are extensively observed in the prior art of the field.

Said retractable guide supports 20, 21 of the bar pusher, which are specifically shown in the attached figures 3, 8 and 9, are structured as holding hooks protruding under the upper half-shells and advantageously allow to hold and guide the bar pusher 16 even when the upper half- shells are in a raised configuration, i.e., not pulled down on their lower counterparts 5.

The retractable guide supports 20, 21 are divided into a group of first retractable guide supports 20 and a group of second retractable guide supports 21 , each group being fixed on a respective longitudinal member 24. Each longitudinal member 24 is transversely guided by a plurality of transverse pins 39, which slide within blind holes 40 integral with the upper supports 9. Each longitudinal member 24 can in fact be driven by an actuator 41, of the pneumatic, hydraulic or electric type, which drives a longitudinal slide 42 whereon a plurality of grooves 43 are provided, within which respective wheels 44 fixed to arms 45, which are integral with the longitudinal members 24, engage. On the longitudinal slide 42 are also provided longitudinal slots within which heads 46, which are integral with the upper supports 9, slide. The above-mentioned elements define a cam mechanism, wherein the operation of the actuators 41 causes the movement of the slides 42 which in turn, through the wheels 44 and the supports 45, move the members 24 between two opposite positions: an extracted position A in which the retractable supports 20, 21 are centered, i.e., placed under the movable portion 10 of the guide channel 6, and a retracted position B in which said retractable supports are not centered with respect to said movable portion 10. On the one hand, the positioning and the special conformation of the retractable supports 20, 21 and of the cam mechanism 42, 43, 44, 45 described above allow the passage of a carriage 25 and of a lateral tab 26 which allow the operation of the bar pusher 16, on the other hand they support and guide said bar pusher 16 even in the conditions in which the movable portion 10 is open or in an intermediate position.

The retractable guide supports 20, 21 may have different conformations. They are preferably made as inserts which can be associated by screw- connection over a centering body of the longitudinal member 24. Preferably, said inserts have different faces with brackets having various shapes for adapting to different diameters of the bar pusher, and can be locked on the centering body with different configurations depending on which face is desired to be used for holding the bar pusher 16.

As mentioned above, said retractable guide supports 20, 21 are functionally divided into first guide supports 20 and second guide supports 21.

The first retractable guide supports 20 are positioned between the front end of the feeder and the clamping device 17. They go into the extracted position A, i.e., into the working position, in the steps in which the bar pusher 16 has to be supported, i.e., when the movable portion of the guide channel 6 is in open or partially open position and the bar pusher 16 is not in the completely backward position. On the contrary, they go into the retracted position B when the bar pusher 16 reaches a completely backward position LI and before the movable portion 10 closes, to avoid interferences with the bar 18 which has been already loaded in the fixed portion 5 in the step of closing the movable portion 10.

The second retractable guide supports 21 are positioned in a rear section of the bar feeder 1, i.e., between the clamping device 17 and the rear end. In said rear section the bar pusher retracts to the completely backward position LI, and the second guide supports 21 are thus maintained in the extracted position A during all the working steps, and can go into the retracted position B only during machine downtime for allowing the retooling of the bar feeder 1, i.e., for allowing the release of the bar pusher 16 into the fixed portion 5 of the guide channel 6 thereby allowing its maintenance or replacement.

As previously mentioned, a main drive 15 integral with the upper supports 9 is provided; said main drive 15 follows thus the movable portion 10 of the guide channel 6 in its movements of opening and closing.

In the preferred embodiment shown in the attached drawings, said main drive 15 is of the traditional type with an electric ratiomotor, comprising a gearwheel 27 which drives a chain 28 which, by interposition of the carriage 25 and of the above-mentioned lateral tab 26, longitudinally drags the bar pusher 16 along the guide channel. The carriage 25 and the chain 28 are suitably contained in a shaped channel 29. Of course, the drive can also be of a different type and still remain within the scope of protection of the present invention. Since the main drive 15 is integral with the upper supports 9 of the upper half-shells, thanks to additional expedients described below, it is possible to perform various steps of the bar change cycle in conditions in which the movable portion 10 of the guide channel 6 is partially or totally open, and this allows to overlap said steps to the others, thereby considerably shortening the total time of the bar change cycle.

The bar feeder 1 further comprises a pre-advancement device 14, which allows to limit the total length and the overall dimensions. In a per se known manner, the pre-advancement device 14 is provided with a pre advancement carriage 31 which goes into the guide channel 6 and whose function is to push the new bar 18 introduced into the fixed portion 5 of the guide channel 6 until it has brought it in front of the gripper 19 of the bar pusher 16, which is in the meantime held by the upper half- shell 10. After re-closing the movable portion 10, and the resulting alignment of the bar pusher 16 held therein with the new bar 18 to be machined, the bar 16 is introduced in the front gripper 19 to the bar pusher 16. In the preferred embodiment shown in the attached figures, the pre advancement device 14 consists of a rodless pneumatic cylinder 30, but it can also be an electric cylinder or a chain drive or another type of drive.

A distinctive feature of the pre-advancement device 14 is the fact that it is movable between a centered position F, in which the pre-advancement carriage 31 is aligned with the fixed portion 5 of the guide channel 6, and an eccentric position G, in which the carriage 31 is offset with respect to the guide channel 6. In particular, the pre-advancement device 14 is in the centered position F when the movable portion 10 is in the opening position, and it is in the eccentric position G when the movable portion 10 is lowered to define the guide channel 6 on the upper part. In this way, after maintaining the centered position F to push the bar 18 into its initial position, the pre-advancement device 14 moves to the eccentric position G and clears the guide channel 6, going back to the backward position in concurrent time. Therefore, in contrast to what happens in the prior art, the closure of the guide channel 6 may occur before the complete return of the pre-advancement device into its backward position.

The pre-advancement device 14 can be moved from the centered position F to the eccentric position G and vice versa by using additional designated control devices to manage its operation separately from the other mechanisms of the feeder.

In the preferred embodiment shown in the attached figures, on the contrary, said movements of the pre-advancement device are advantageously obtained by suitable rotatable arms 32 connected to the shaft 8 by a transmission leverage 33. The fact that they are both operated from the same shaft 8 allows to synchronize the position of the movable portion 10 of the guide channel 6 and that of the pre advancement device 14, thereby avoiding possible mechanical interferences and at the same time reducing the time of bar change cycle, because it is not required to wait for permissives from microswitches that signal their position or from the control electronics. The clamping device 17, which is also integral with the movable portion 10, can take various shapes, all included in the scope of protection of the present invention.

In the preferred embodiment shown in the attached figures, said clamping device 17 comprises a rotatable actuator 34 that, by means of a pinion 35, drives in opposite direction two racks 36, which are integral with two jaws 37 provided with clamping blades 38. When the clamping blades 38 close on the bar, the backward movement of the bar pusher 16 allows the extraction of the residual piece 13; on the contrary, the advancement of the bar pusher 16 in the opposite direction allows the introduction of a new bar 18 in the gripper 19 of said bar pusher 16. The operation of the rotatable actuator 34 may be pneumatic, hydraulic or of other type.

As a consequence of the above-mentioned technical distinctive features, the main steps of the bar change cycle can occur so as to overlap to each other, according to a method of operation described below.

Once the machining of the bar 18 has been completed, the method comprises a step of moving backward the bar pusher 16 with the bar residual piece 13 remaining from the machining until a recovery position H has been reached, wherein in said recover position H, observable in Figure 4, the bar pusher 16 and the residual piece 13 are entirely contained within the bar feeder. Starting from this recovery position H, the movable portion 10 of the guide channel 6 can start to go into the raised position. Despite the raising of the movable portion 10, the bar pusher 16 and the residual piece 13 still continue their return stroke towards the backward position, without having to stop or slow down their motion, because they are supported by the retractable guide supports 20, 21.

During completion of the opening of the movable portion 10 and of the backward movement of the bar pusher 16, a new bar 18 is selected and let fall into the fixed portion 5 which is remained free; in the meantime, the pre-advancement device 14 moves to the centered position F i.e., the pre-advancement carriage 31 aligns with the axis of the new bar 18.

When the pre-advancement device 14 is in the centered position F and the new bar 18 is in place in the fixed portion 5 of the guide channel 6, according to the configuration shown in Figure 4, the pre-advancement of the bar 18 begins, i.e., the pre-advancement carriage pushes the bar towards the front part of the fixed portion 5. In the meantime, the bar pusher 16 reaches a backward position L2.

At this time, according to what is shown in Figure 5A, the residual piece 13 is locked by the clamping device 17, which is also at the open movable portion 10 of the guide channel 6. The subsequent backward movement of the bar pusher 16 into a completely backward position LI causes the extraction of the residual piece 13 from the bar pusher 16. The opening of the clamping device 17 achieves the expulsion of the residual piece 13 through the chute 12. In the meantime, concurrently, the step of pre advancement of the bar 18 comes to an end.

In the next step, shown in Figure 6, the closure of the movable portion 10 of the guide channel 6 and the simultaneous movement of the pre advancement device 14 into the eccentric position G begin. The bar pusher 16 becomes then aligned with the new bar 18 to be machined.

Then, the clamping device 17 closes, and thus locks the bar 18 into place, while the bar pusher 16 is brought from the completely backward position L2 to the backward position LI, thereby causing the insertion of the bar 18 in the gripper 19.

The clamping device 17 is then opened and the bar pusher 16 is further advanced, so as to bring the bar 18 into a working position beyond the front end of the bar feeder 1. At this time, the bar change cycle is finished and the lathe machining of the new bar 18 which has been fed starts.

The final result, as highlighted in the attached Figures 11 and 12, is the clear overlapping and thus the compaction of many steps of the bar change cycle with a considerable optimization and reduction of the total time of cycle, up to its halving, compared to the feeder that are currently used.

Obviously, a person skilled in the art, in order to satisfy any specific requirements which might arise, may make numerous modifications and variations to the bar feeder and the method of operation described above, all of which are however contained within the scope of protection of the invention, as defined by the following claims.

Claims

1. Bar feeder (1) for feeding a tool machine, comprising: a guide channel (6) arranged to receive a bar (18) to be fed to a tool machine, said guide channel (6) comprising a fixed portion (5) and a movable portion (10) movable between a closed position, next to the fixed portion (5) and an open position away from the fixed portion (5); a bar pusher (16), provided at the front with a gripper (19) to constrain the bar (18) and movable within said guide channel (6) to push the bar (18) in a partially extracted working position with respect to the bar feeder (1); a main drive

(15) for longitudinally moving said bar pusher (16) along said guide channel (6); and clamping means (17) adapted to lock the longitudinal sliding of the bar (18) to allow the engagement of the new bar (18) to be machined on the gripper (19) of the bar pusher (16) and the disengagement of the residual piece (13) at the end of the machining; wherein said bar pusher (16) is slidingly constrained to said movable portion (10) of the guide channel (6) and said clamping means (17) are configured to act on the residual piece (13) engaged in said bar pusher

(16) housed in the movable portion (10) when said movable portion (10) is in the open position.

2. Bar feeder (1) according to claim 1, wherein said clamping means

(17) are integral with the movable portion (10) of the guide channel (6) in its relative motion with respect to the fixed portion (5) or they comprise a first clamp acting at the fixed portion (5) to lock the bar (18) upon engagement on the gripper (19) and a second clamp acting at the movable portion (10) lo lock the residual piece (13) upon release from the gripper (19).

3. Bar feeder (1) according to any one of the preceding claims, comprising at least guide supports (20, 21) arranged to hold the bar pusher (16) at the bottom when the movable portion (10) is in the open position.

4. Bar feeder (1) according to claim 3, wherein said guide supports (20, 21) comprise first guide supports (20) arranged at the front with respect to the clamping means (17) and second guide supports (21) arranged at the rear with respect to the clamping means (17), said first guide supports

(20) being retractable independently from said second guide supports

(21) .

5. Bar feeder (1) according to one of claims 3 or 4, wherein at least part of said guide supports (20, 21) are mounted on a longitudinal member (24), said guide supports (20, 21) being retractable thanks to a cam mechanism (42, 43, 44, 45) that defines a transversal movement of the longitudinal member (24).

6. Bar feeder (1) according to one of claims 3-5, wherein each guide support (20, 21) has different faces with alternative profiles intended for different diameters and/or configurations of bar pusher (16) and may be alternatively mounted with a different face facing towards the bar pusher (16).

7. Bar feeder (1) according to any one of the preceding claims, wherein the main drive (15) is integral with the movable portion (10) of the guide channel (6) in its relative motion with respect to the fixed portion (5) .

8. Bar feeder (1) according to any one of the preceding claims further comprising a pre-advancement device (14) arranged to bring the bar (18) from an initial position thereof of introduction into the fixed portion (5) of the guide channel into an advanced position thereof with respect to a start-stroke position of the bar pusher (16), said pre-advancement device (14) being driven by a secondary actuator that is independent with respect to the main drive (15).

9. Bar feeder (1) according to claim 8, wherein said pre-advancement device (14) comprises a pre-advancement carriage (31) arranged to push the bar (18) along the fixed portion (5) of the guide channel (6), said pre advancement carriage (31) being movable between a centered position (F), in which the pre-advancement carriage (31) is aligned with the fixed portion (5) of the guide channel (6) and is operational on said bar (18), and an eccentric position (G), in which the carriage (31) is offset with respect to the guide channel (6), wherein said pre-advancement carriage (31) moves to the centered position (F) when said movable portion (10) of the guide channel (6) is in the open position, and to the eccentric position (G) when said movable portion (10) of the guide channel (6) is in the closed position, said eccentric position (G) allowing a return of the pre advancement carriage (31) from a front end-stroke position to a rear end- stroke position, without interfering with the bar pusher (16) when the movable portion (10) is in the closed position on said fixed portion (5) of the guide channel (6).

10. Method of operation of a bar feeder (1) comprising the steps of: introducing a bar (18) into a fixed portion (5) of a guide channel (6) of a bar feeder (1); bringing a movable portion (10) of the guide channel (6) into a closed position above said fixed portion (5) of the guide channel (6); locking the longitudinal stroke of the bar (18) through clamping means (17); advancing a bar pusher (16) along the guide channel (6), so as to engage said bar (18) on a front gripper (19) of the bar pusher (16); pushing, by means of the bar pusher (16), said bar (18) into a working position on a tool machine at least partially extracted from the bar feeder (1); once the machining of the bar has been completed (18), bringing said bar pusher (16) back, with the residual piece (13) still engaged on the gripper (19), along said movable portion (10) of the guide channel (6) until a backward position (L2) has been reached; once said backward position (L2) of the bar pusher (16) has been reached, locking said residual piece (13) through said clamping means (17) and bringing the bar pusher (16) back along said movable portion (10) up to a further backward position (LI), thus freeing the residual piece (13) from the gripper (19); wherein at least said step of locking said residual piece (13) and of bringing the bar pusher (16) back until the further backward position (LI) has been reached are made with the movable portion (10) of the guide channel (6) open, thus keeping the fixed portion (5) of the guide channel (6) free for the possible introduction of a new bar (18).