WO2015074723A1

WO2015074723A1 - Bar feeder

Info

Publication number: WO2015074723A1
Application number: PCT/EP2013/074591
Authority: WO
Inventors: Frank Antonin REISSER; Karim OUIDIR
Original assignee: Lns Management Sa
Priority date: 2013-11-25
Filing date: 2013-11-25
Publication date: 2015-05-28
Also published as: TW201532715A; EP3074163A1; TWI641435B

Abstract

According to the present invention, the bar feeder for feeding longitudinal bars to and/or from a processing machine comprises a moveable pusher (3), which is connectable to a bar (1), and a drive unit (5) for moving the pusher (3) subject to a predetermined required movement of the pusher. The pusher (3) is coupled with the drive unit (5) by a float mount (6), which comprises at least one attenuator (7) for dampening a relative movement between the pusher (39 and the drive unit (5).

Description

Bar feeder

Technical domain of the invention

The present invention relates to a bar feeder for feeding a longitudinal bar into a further processing machine, like a lathe, in

synchronization with a movement of the machine.

Background Art

In conventional processing machines for further processing of longitudinal bars, like metal rods, a bar is fastened in a headstock, while tools of the machine for processing the bar are fixed. The headstock may move in axial direction of the bar to position the bar for further processing, and may revolve to reach the necessary revolutions per minute for a turning process of the machine. As a result, the whole bar moves back and forth, while rotating, along the axis by several millimeters for each bar.

The bars are fed by a bar feeder to the processing machine. To do so, the bar feeder needs to know the current position of the bar to be able to perform its tasks. Therefore, a pusher of the bar feeder is equipped with a rotating finger chuck, wherein the bar is inserted and firmly held. As a result, the pusher has to replicate the same movements as the bar to prevent from losing the bar when moving forward, and prevent from destructing bar when moving backward. To effectively replicate the axial movement, the pusher's drive is either mechanically connected to the headstock by a clutch to provide a mechanical synchronization, or a measuring device measures the headstock movements, and orders the pusher's drive, typically a servo drive, to move by the same distance and direction to provide an electronic synchronization.

For example in EP 0559586 a bar feeder for a lathe is shown, which comprises a bar guide and a pusher mounted so that the bar guide can slide within the pusher. A flexible cable is secured on its first end to the pusher and on its second end in a reserve cable guide tube. The cable is guided around a pulley in a u-shape and is pressed or released on the surface of the pulley by presser rollers, which are driven by an electric motor and hysteresis coupler in accordance to a position of the pusher or a bar respectively. In GB 1471045 a bar feeder is disclosed which uses a servo motor to control a chain connector between a pusher and a bar guide. The pusher is disengageably connected to a bar gripper by a pre-tensioning spring.

A mechanical synchronization has virtually no offset between the movement of the headstock and the replication on the pusher position, but is unable to handle acceleration and deceleration ramps, or fine tune the torque to apply to keep the bar under slight tension. Additionally, engaging and disengaging a clutch requires more time within the production cycle. The use of servo drives offer total control on the positioning accuracy, speed and smoothness of the bar but have the disadvantage of being relying on an external measuring device to know the distance and direction of the move to be made, and herewith add a subsequent error into the positioning accuracy, the offset between the current motor position of a stator and the position to reach is always varying with new information. This translates into a delayed reaction time of the motor where the material is either compressed or pulled, raising the risk of failure, especially on thin bars.

Summary of the invention

It is therefore an object of the present invention to provide a bar feeder and a bar processing system that provide an improved control of a relative movement between the bar feeder and a processing machine, that allows for rapid production cycles and to keep the bar under slight tension during the processing, that increase accuracy of the bar position, simplify bar handling during process and that are simple to install and to control in use.

These and other objects are fulfilled by a bar feeder and a bar processing system according to independent claims 1 and 1 1 . Advantageous features and preferred embodiments of the bar feeder and the bar processing system according to the invention are disclosed in dependent claims. According to the present invention a bar feeder for feeding longitudinal bars to and/or from a processing machine comprises a moveable pusher, which transports the bars in direction to and/or away from the processing machine, and a drive unit for moving the pusher subject to a predetermined required movement of the pusher. The pusher can be connected and disconnected to and from a bar, so that the bar follows a movement of the pusher. Preferably the pusher is of longitudinal shape and comprises a rotatable connection for the bar at a first end. Thus a bar can be connected to the pusher in alignment with the longitudinal axis of the pusher. The predetermined movement of the pusher may serve to feed a bar to the processing machine or to remove a bar from the processing machine. Also the predetermined movement may be defined by a movement to adjust the position of the pusher relative to the processing machine, while the bar is fed into the machine and in particular while the bar is processed by the machine. The pusher is coupled to a drive unit, which basically drives the pusher along an axial direction of the pusher towards and away from the processing machine. The pusher is coupled with the drive unit by a float mount, which comprises at least one attenuator for dampening or retarding a relative movement between the pusher and the drive unit. Such relative movement between pusher and drive unit is for example the predetermined movement of the pusher as mentioned above or may be some unexpected deviation of a defined process movement during bar processing.

The bar feeder is advantageously used in a bar processing system with a processing machine, that comprises a fastener, like a headstock, for receiving a bar, which fastener moves and/or revolves for processing of the bar in the processing machine. The pusher of the bar feeder is aligned with the fastener and is coupled to the movement of the fastener by a bar to be processed by the processing machine. The connection between bar and pusher is releasable, for example a clamp connection like a finger chuck.

While the pusher is connected to the bar, the pusher executes the same movement as the bar and vice versa. That is for example when the pusher drives the bar to be fed into the processing machine or the pusher is driven by the bar, which itself is driven by the processing machine, e. g. by the fastener. As explained above in a processing machine, for example a lathe, the bar is arranged slideably and rotatetably to allow the processing of the bar by stationary tools of the processing machine. The pusher connected to the bar follows the movement of the bar. This movement is first absorbed by the at least one attenuator of the float mount. Then the movement may be transferred to the drive unit. The time of retardation of the pusher movement can be utilized by the drive unit to react on a movement of the bar and drive the pusher subject to a required movement, for example to correct the position of the pusher, to tension or compress the bar, while the bar is fastened in the fastener, or even to feed or remove the bar from the processing machine. The retardation softens the bar movement in relation to the drive unit of the bar feeder. Also the retardation provides time for the drive unit to react on the bar movements. Thus the bar feeder and the bar processing unit according to the invention allow a precise control of the driving of the pusher of the bar feeder as required for correct processing of the bar. They enable a fine tuning of the position of the pusher relative to the processing machine and the drive unit, without the risk of damaging the bar, the processing machine or the bar feeder and without a time consuming disengagement of the bar.

The float mount of the bar feeder preferably is designed for floating movement of the pusher relative to the drive unit in axial direction of the pusher, which direction usually corresponds to the feeding direction to feed a bar to the processing machine and also to the axial orientation of the bar.

Preferably, the pusher and the drive unit are stationary mounted relative to each other in rotational direction and in radial direction of the pusher. That means the float mount allows a floating movement between pusher and drive unit only in direction, which is the axial direction of the pusher. This ensures precise guiding of the pusher relative to the drive unit and the processing machine.

In one embodiment the attenuator is designed as at least one mechanical spring, in particular a coil spring. Alternatively, a hydraulic attenuator may be used, for example. But the mechanical spring offers a simple construction of the bar feeder. Generally the overall spring constant of the at least one mechanical spring depends on the forces exerted on the bar and the speed of processing the bar.

For example, the coil spring is arranged around an extension, which extends of one the pusher or the drive unit in moving direction of the pusher. The coil spring is placed between a first block on the extension and a second block on the other one of pusher and drive unit, which does not comprise the extension. When the pusher is moved relative to the drive unit within the float mount, the spring is compressed or stretched between the blocks.

In one embodiment the float mount comprises stoppers for an abutment between the pusher and the drive unit in a first and a second end position in each axial direction. In the end positions a force of the drive unit or the processing machine on the pusher is not dampened or retarded because of the direct abutment in the respective direction. This enables a fast force transmission on the pusher and the bar respectively for example, when the bar is fed to or removed from the processing machine. The float range of the float mount can be defined by the choice of a specific spring constant for a given maximum force applied to the bar or pusher by the processing machine or the drive unit. The range can on the other hand also be defined by the geometry of the design of the float mount. For example stoppers of the float mount as mentioned above can limit the float range within the float mount. The stoppers may for example be designed as abutment steps, stop walls or the like on the pusher which interact with counter steps, counter walls and so on on the drive unit.

In one embodiment the float mount of the bar feeder according to the invention comprises an elongated element, which is for example coupled to the drive unit. The elongated element comprises at least one slot hole, which may be a through hole or a blind hole. Furthermore the float mount comprises at least one pin, for example extending from the pusher and being slideably arranged in a slot hole. Thus there are as many pins as slot holes. The at least one slot hole is longitudinally orientated in moving direction the pusher relative to the drive unit. Thus the pin reaching into the slot hole can move along the length of the slot hole from one end to the other. The ends of the slot define the stoppers for the relative movement. And the sides of the slots define a guiding for the pins in moving direction of the pusher.

In another embodiment the float mount of the bar feeder according to the invention comprises a longitudinal inner part and a sleeve-like outer part. The inner part may be coupled to the drive unit and the outer part may be coupled to the pusher or the other way round. The outer part slideably receives the inner part. The inner part preferably extends at least at one end out of the outer part. The at least one attenuator is arranged between the inner part and the outer part. The attenuator is for example arranged between an abutment wall on the inner part and a counter abutment wall on the outer part. Thus the attenuator dampens a movement of the walls towards and from each other. Preferably the attenuator is realized by at least one coil spring, which is arranged around the inner part between an abutment on the inner part and a counter abutment on the outer part. The coil spring may be arranged within the outer part or may by located on the extending end of the inner part.

The drive unit of the bar feeder may be a servo motor or a mechanical drive device as commonly used for bar feeders or a combination thereof. A control unit may be provided for synchronizing a movement of the drive unit driving the pusher and the fastener of the processing machine relative to each other. Advantageously, the retardation time due to the damping of the movement as mentioned above is used by the control unit to synchronize the movement between drive unit and fastener. Also a sensor unit may be provided for determining the position of the pusher and the fastener respectively. The sensor unit may provide a position signal to the control unit or to the drive unit directly as well as to the processing machine for controlling a production position in which the bar is processed by the machine.

In a preferred embodiment of the bar processing system according to the present invention the drive unit is controlled such that in a production position for processing the bar, the pusher is in a middle position of the float mount between a first and a second end position. In the middle position the attenuator may or may not be pre-stressed in axial direction of the pusher. From the middle position the pusher may be deflect the same distance within the float mount in one and the opposite axial direction. Thus deviations of a correct production position can easily and fast be adjusted by a movement of the pusher, which is induced by the drive unit.

Brief description of the drawings

An exemplary embodiment of the invention will be illustrated in the following drawings, which merely serve for explanation and should not be construed as being restrictive. The features of the invention becoming obvious from the drawings should be considered to be part of the disclosure of the invention both on their own and in any combination. The drawings show:

Fig. 1 : a schematic view of one example of a bar processing system

according to the invention,

Fig. 2a-b: a schematic view of one example of a bar feeder according to the present invention in a first position (fig. 2a) and a second position (fig. 2b), and

Fig. 3a-c: a longitudinal cut of one example of a bar feeder according to the present invention in a first position (fig. 3a), a second position (fig. 3b), and a third position (fig. 3c).

Detailed description of the preferred embodiments

Figure 1 shows in a schematic way the essential parts of an example of a bar processing system according to the present invention. A bar 1 is fixed in a fastener 2, which is for example a headstock, of a bar process machine. Other details of the bar processing machine may be designed as commonly know and therefore are not shown in the figures. Basically the processing machine may work as a lathe comprising a rotation drive for revolving the fastener with the bar. Furthermore the bar processing machine may comprise one or more tools for processing the bar to a final or intermediate product. For example, there may be a grinding tool, a milling tool or the like.

The bar 1 is held by a bar feeder. The bar feeder comprises a moveable longitudinal pusher 3, which comprises a finger chuck 4 at one end, that is connected to an end of bar 1 . The pusher 3 and the bar 1 are aligned along a common axis. The finger chuck 4 is rotatable around the rest of the pusher in conventional manner, so that finger chuck 4 revolves with the bar 1 while the pusher does not rotate. Instead of a finger chuck any other suitable coupling can be used to couple the bar 1 rotatable to the pusher 3. Further, the bar feeder comprises a drive unit 5 for moving the pusher 3 subject to a predetermined required movement of the pusher. The drive unit 5 is a conventional servo drive that is coupled to the pusher 3 to move the pusher in an axial direction of the pusher. According to the invention the pusher 3 is coupled with the drive unit 5 by a float mount 6, which comprises at least one attenuator 7 for dampening a relative movement between the pusher 3 and the drive unit 5. As shown schematically in figure 1 the drive unit 1 comprises an elongated element 8, like a rod or a sleeve, which receives a protrusion 9 of the pusher 3 in a floating manner, for example in a slot in the elongated element. The elongated element is shown as a coil spring in form of a screw spring, which is placed between a first block 10 of the elongated element 8 and a second block 1 1 of the pusher protrusion 9.

As indicated by arrows in figure 1 the bar 1 is moved in axial direction by the fastener 2, for example during processing the bar by the tools of the processing machine. The axial movement is transferred to the pusher 3, which moves in axial direction of the elongated element 8, while the protrusion 9 floats within the elongated element 8.

Figures 2a and 2b show different positions of the function of the bar feeder. In figure 2a the bar is for example fed to the processing machine and the fastener respectively by the bar feeder. The drive unit 5 pushes the elongated element 8 in forward direction towards the processing machine. The protrusion starts sliding within the float mount until it stops at a stopper 12 of the elongated element 8. Now the protrusion 9 abuts on the elongated element 8 in a first end position within the float mount. Thus the pusher 3 is directly pushed forward by the drive unit 5. The attenuator 7 is stretched and pulls on the pusher 3. A similar situation occurs when the pusher pulls the bar back out of the fastener of the processing machine after the processing is finished. In this case the second block 1 1 rests against the first block 12 and fully compresses the attenuator 7.

In figure 2b the pusher 3 and the drive unit 5 are shown in a production position, in which the bar 1 is readily positioned for processing. In this position the float mount keeps the protrusion 9 essentially in the middle of the slot of the elongated element 8. Thus the protrusion can move to both axial directions during the processing of the bar 1 . An axial processing movement of the bar leads to a deviation of the protrusion 9 within the elongated element 8. But the movement is dampened by the attenuator 7 relative to the drive unit 5, which leads to a retardation time for the transfer of the a moving force to the drive unit 5. Within the retardation time the drive unit can adjust the position of the elongated element 8, so that the protrusion 9 again is essentially in the middle of the slot of the elongated element 8.

The floating mount 6 between the drive unit 5 and the pusher 3 allows for some time for the servo drive to react on the bar movement. The float mount 6 temporarily compensates the reaction time of the drive unit 5 by immediately moving the pusher 3 according to the bar's 1 new position, and then letting the drive unit 5 reach this new position. Furthermore, the float mount 6 allows the drive unit 5 to pull the bar 1 backward or forward, measure a torque of the attenuator 7 when the bar is fully pulled or pushed, and adjust the float mount or the elongated element 8 respectively. This effectively protects the bar 1 from being lost by overpull, or destroyed by overpush. Also by changing dimensions and design of the elements of the float mount, it is easy to adapt the bar feeder to different bar comprising different stiffness or length.

Figures 3a to 3c show a structural example of parts of a bar feeder regarding the function of the float mount 6. Same parts are described by same reference numbers as in the schematic example of figures and 2. The elongated element 8 comprises two slot holes 13. The pusher 3 is connected to the protrusion 9 by two screws, which extend as pins 14 in radial direction of the pusher 3 from the protrusion 9. Furthermore, another screw extends in longitudinal direction of the elongated element 8 as a bolt 15 comprising the first block 10. The second block 1 1 is attached to the protrusion 9 and extends in radial direction. The second block 1 1 comprises a through hole, which slideably receives the bolt 15. Therefore, the bolt 15 extends from the elongated element 8 through the second block 1 1 . An attenuator in form of a coil spring 7 is wound around the bolt 15 between the first block 10 and the second block 1 1 . To mount the coil spring 7 the spring is thread on the bolt 15 and the bolt 15 is plugged through the through hole and screwed into the elongated element 8.

The slot holes 13 run in moving direction of the pusher and the drive unit when moved relative to each other. The slot holes 13 and the pins 14 together establish the float mount. Each slot hole comprises a first stopper 16 on one end of the slot and a second stopper 17 on the opposing end of the slot. The stoppers 16 and 17 stop the floating of the pins within the slot holes 13 in a first and a second end position. The distance between the first stopper 16 and the second stopper 17 is smaller than the distance between the first block 10 and the second block 1 1 . Therefore the stoppers 16 and 17 limit the float range of the float mount 6.

In figure 3a the bar feeder is in a push position. The drive unit 5 pushes the pusher 3 in longitudinal direction forward to a processing machine and for example into a fastener of the machine. The pins 14 abut against the first stoppers 16 to transfer the push movement to the pusher. T he coil spring 7 is stretched.

In figure 3b the bar feeder is in a pull back position. The drive unit 5 pulls the pusher 3 back and for example the bar out of the processing machine. The pins 14 abut against the second stoppers 17 to transfer the pull movement to the pusher 3. The coil spring 7 is compressed. In figure 3c the bar feeder is in a production position. The pins 14 are located in the middle of the slot holes 13. The coil spring is preferably relaxed. In the production position the pusher can hold a bar under processing and follow axial movements of the bar. The movement is transferred to the block 1 1 which acts on the coil spring 7, which in turn dampens the movement. The retardation time of the transfer of the movement is used by the drive unit to readjust the float mount by axially moving the elongated element 8 so that the pins 14 are in the middle of the slot holes 13 again. If necessary for the processing of the bar, the bar can also be tensioned by the force of the coil spring 7. To do so the elongated element 8 is positioned relative to second block 1 1 so that the coil spring exerts a force on the first block 10, which transfers the force on the pusher 3.

Reference Numbers

bar

fastener

pusher

finger chuck

drive unit

float mount

attenuator

elongated element

protrusion

first block

second block

stopper

slot hole

bolt

first stop

second stop

Claims

1 . Bar feeder for feeding longitudinal bars to and/or from a processing machine comprising a moveable pusher (3), which is connectable to a bar (1 ), and a drive unit (5) for moving the pusher (3) subject to a

predetermined required movement of the pusher, characterized in that, the pusher (3) is coupled with the drive unit (5) by a float mount (6), which comprises at least one attenuator (7) for dampening a relative movement between the pusher (39 and the drive unit (5).

2. Bar feeder according to claim 1 , characterized in that the float mount (6) is designed for a floating movement of the pusher (39 relative to the drive unit (5) in an axial direction of the pusher

3. Bar feeder according to claim 1 or 2, characterized in that the float mount (6) is designed such that the pusher and the drive unit (5) are stationary mounted relative to each other in rotational direction and in radial direction of the pusher (39.

4. Bar feeder according to one of the preceding claims,

characterized in that the attenuator (7) is designed as at least one mechanical spring, in particular a coil spring.

5. Bar feeder according to claim 4, characterized in that the at least one coil spring is arranged around an extension (15), which extends of one of pusher (3) and drive unit ()15 in moving direction of the pusher, wherein the coil spring is placed between a first block (10) on the extension and a second block (1 1 ) on the other one of pusher and drive unit.

6. Bar feeder according to one of the preceding claims,

characterized in that the float mount comprises stoppers (16; 17) for an abutment between the pusher and the drive unit in a first and a second end position in each axial direction.

7. Bar feeder according to one of the preceding claims,

characterized in that the flout mount (6) comprises an elongated element (8) with at least one slot hole (13), and at least one pin (14) slideably arranged in a slot hole, wherein the at least one slot hole is longitudinally orientated in moving direction the pusher (3) relative to the drive unit (5).

8. Bar feeder according to one of the preceding claims,

characterized in that the drive unit (5) comprises a servo motor.

9. Bar processing system comprising a bar feeder according to one of the preceding claims and a processing machine, wherein the processing machine comprises a fastener (2) for receiving a bar (1 ), which moves and/or revolves for processing of the bar (1 ), and wherein the pusher (3) of the bar feeder is aligned with the fastener (2) and is designed to be coupled to the movement of the fastener (2) by a bar (1 ) to be processed by the processing machine.

10. Bar processing system according to claim 9, characterized in that a control unit is provided for synchronizing a movement of the drive unit and the fastener relative to each other.

1 1 . Bar processing system according to claim 10, characterized in that the drive unit is controlled such that in a production position for processing the bar, the pusher (3) is in a middle position of the float mount (6) between a first and a second end position.