Removing a processed part

A machine tool is provided for processing a workpiece, e.g., a metal sheet. The machine tool comprises at least one support configured to, in a support position, support a part of the workpiece on an upper surface, the part being completely separated from the workpiece, and a motion unit for moving the support downwards out of the support position into a discharge position located underneath the support. The motion unit is configured to accelerate the support, at least in a region of the part lying thereon, out of the support position along a gravitational direction with an acceleration which is greater than an acceleration of the part in the gravitational direction, and to move the accelerated support into an open position located outside a path of movement of the part at a speed such that the workpiece part attains the discharge position in free fall.

CROSS REFERENCE TO RELATED APPLICATION

This application claims priority under 35 U.S.C. §119(a) from EP Application No. 07 012 866.5, filed Jun. 30, 2007, the entire contents of which are hereby incorporated by reference.

TECHNICAL FIELD

This invention relates to processing a workpiece, and more particularly to moving a processed part of the workpiece into a discharge position.

BACKGROUND

During processing of a workpiece with a machine tool, for example, a laser cutting device or a punching device, the processed parts of the workpiece need to be removed to allow the processing of the next part. Exemplary mechanisms for removing a processed part are disclosed, for example, in the Japanese Patent publications JP 7214359 and JP 10118879.

SUMMARY

In one aspect, a machine tool for cutting a preferably plate-shaped workpiece, especially a metal sheet, includes at least one support, on the upper surface of which a workpiece part lies in a process position. The workpiece part has been completely cut out of the workpiece. The machine tool has a motion unit for moving the support downwards out of a support position in order to move the workpiece part into a discharge position located underneath the support.

The motion unit is further designed to accelerate the support, at least in the region of the workpiece part lying thereon, out of a support position in the gravitational direction with an acceleration which is greater than the acceleration of the workpiece part in the gravitational direction, and to move the accelerated support into an open position located outside the path of movement of the workpiece part at a speed such that the workpiece part attains the discharge position in free fall.

In some embodiments, the workpiece part moves into the discharge position in free fall. In relation to a gliding or sliding movement, a free-fall movement has the advantage that it usually represents the fastest possible way of moving the workpiece part into a discharge position outside the machining region. To allow a free-fall movement, the support can be accelerated downwards out of the support position more quickly than the workpiece part itself so that the latter is lifted from the support. Thereby, the reliability of the process can be increased because the workpiece part cannot be shifted laterally and can thus be prevented from being held back by the remainder of the workpiece. The support is subsequently moved out of the path of movement of the workpiece part into an open position typically located laterally thereof. Thereby, the workpiece part is prevented from striking the support after having been lifted therefrom and can attain the discharge position unimpeded.

In some embodiments, at least one, e.g., each support can be mounted so as to be pivotable about a rotation axis extending, for example, at a right angle to the gravitational direction. The support can then be horizontally orientated in the support position so that the workpiece part can lie on its upper surface. The support can be pivoted downwards about the rotation axis in order to move the workpiece part into the discharge position. To allow free fall of the workpiece part, the supporting region of the workpiece part can be arranged eccentrically to the rotation axis so that when the support is pivoted about the rotation axis, the support can be accelerated with a greater acceleration than the workpiece part itself. The acceleration of the support out of the support position in the gravitational direction can increase with the distance from the rotation axis, so that the greater the distance of the supporting region from the rotation axis, the smaller the torque can be chosen for accelerating the support.

In some embodiments, at least one, e.g. each support, can be motionally coupled to the motion unit via a connecting piece which acts on the support eccentrically to its rotation axis. Then, the motion unit does not act directly on the rotation axis of the support. A lever effect can be produced by the connecting piece, and the synchronous pivoting of a plurality of supports can be facilitated, as will be described below.

In some embodiments, the motion unit can have at least one guide which is displaceably guided in the gravitational direction and on which the connecting pieces are displaceably guided in a linear manner preferably at right angles to the gravitational direction. By moving the guide in the gravitational direction by means of a common drive, the connecting pieces and with them the supports can be synchronously pivoted. The connecting pieces can be positively guided on the guide and can be displaced along the guide, e.g., in a horizontal direction, during the displacement of the guide in the gravitational direction.

In some embodiments, the connecting pieces can be rotatably mounted on the supports and non-rotatably mounted on the common guide. During the pivoting movement of the supports, this can permit parallel displacement of the connecting pieces, but does not permit rotational movement.

In some embodiments, a slide can be provided on at least one of the connecting pieces and projects into the path of movement of the free-falling workpiece part at least in the open position of the support. Then, during the pivoting movement of the support, the slide can be moved downwards and laterally, whereby the slide can project into the path of movement in the open position of the support without additional aids. The provision of the slide can be advantageous, for example, when a constructional unit such as a suction tube is mounted within an area of the path of movement because, the unit can be covered by the slide in order to prevent the workpiece part from striking the constructional unit.

In some embodiments, a fixed slide can be provided for removing the workpiece part from the discharge position. The fixed slide can adjoin the slide mounted on the connecting piece and the two together can delimit the path of movement of the workpiece part downwards, and, e.g., determine the discharge position that the workpiece part attains in free fall.

In some embodiments, the or, e.g., each support can be lowered in the gravitational direction in a linear movement for acceleration out of the support position, wherein the linear movement can be preferably effected over a distance of at most 5 mm, in particular at most 2 mm. For acceleration of the support, the latter can be first displaced in a parallel manner in the gravitational direction, whereby the workpiece part is lifted from the support. The support can subsequently be moved out of the path of movement of the workpiece part in the gravitational direction in a variety of ways, e.g., by displacing the support at right angles to the gravitational direction. The linear movement can further be followed by the above-described pivoting movement of the support about a rotation axis to move the support into the open position.

In some embodiments, the or, e.g., each support in the support position can be biased in the gravitational direction by a biasing means. Great acceleration out of the support position can be generated by the bias. The bias can be produced by applying a force counter to the gravitational direction. The force pushes the supports upwards against a spring force or hydraulic force acting in the gravitational direction.

In some embodiments, the motion unit can have a common drive for synchronously pivoting the supports and, e.g., for synchronously moving the supports during the linear movement. By means of the synchronous pivoting movement, it is possible to prevent a transverse force being exerted on the workpiece part due to the workpiece part being lifted more quickly from one of the supports than from the other during acceleration of the workpiece part out of the support position. Furthermore, costs can be saved by using a common drive for both the pivoting and the linear movement.

In some embodiments, the motion unit can be designed to accelerate the or, e.g., each support in the gravitational direction with an acceleration which is greater than the acceleration due to gravity and is preferably at least twice, in particular at least three times the acceleration due to gravity. A force acting in the gravitational direction in addition to the gravitational force is usually not exerted on the workpiece part in the support position, so that the workpiece part can be accelerated out of the process position with the acceleration due to gravity. However, the support should then be accelerated with a higher acceleration in order to lift the workpiece part from the support. It can be advantageous that a high acceleration acts on the support at least during the first phase of movement because then the support can subsequently be removed from the path of movement of the workpiece part at a lower speed.

In some embodiments, two supports can be provided which are mounted on opposite sides so as to be pivotable about preferably parallel, spaced rotation axes. The falling distance of the workpiece part from the support position to the discharge position can be at least about the width of the support perpendicularly to the rotation axis because the support can usually be pivoted through 80° or more in order to attain the open position located outside the path of movement. The width of the workpiece parts that can be moved into the discharge position is limited by the width of the support. By providing two opposing supports, the width of the workpiece parts that can be moved into the discharge position can be increased without also increasing the falling distance and accordingly the falling time.

In some embodiments, a suction opening can be provided in the support for the removal, by suction, of gases which are produced during the cutting process and/or of waste material. The suction opening can usually be arranged in a machining position of the machine tool, e.g. underneath a laser machining head, and can serve to remove waste material and gases generated during the laser machining of the workpiece. The suction opening can usually be connected to a suction arrangement via a suction tube arranged below the support. When the support is moved into the open position, the suction tube may be in the way and can therefore be moved downwards, e.g., by means of the above-described drive. The slide fixed to the connecting piece can further be dimensioned to cover the opening of the suction tube when the support is in the open position.

In some embodiments, at least one sensor, e.g. at least one light barrier, can be provided for detecting when the workpiece part has attained the discharge position. As soon as the attainment of the discharge position has been detected, the support or the supports can be moved back from the open position into the support position and the machining of the workpiece can be continued. The idle time of the machine tool can thereby be reduced and the reliability of the process can be simultaneously increased when, in the absence of the detection signal, an error signal is generated such that, e.g. further machining is temporarily stopped in order to avoid damage. A series of light barriers can be used which can arranged side by side and form a light grid for monitoring a two-dimensional area at the discharge position.

In some embodiments, the support can in the support position at least partly close an opening in a machining table of the machine tool. For example, the support can be horizontally orientated in the support position and can be arranged at the level of the machining table. However, the support position can optionally also be defined at a position lower than the surrounding machining table, e.g., if the support with the workpiece part lying on its upper surface is initially to be slowly lowered.

In some embodiments, at least one support can be fixed to a displacement arrangement for displacing the support along the machining table. Then, at least one of the supports lying opposite the movable support can be mounted on the machining table. By means of the displacement arrangement, the movable support can be moved away from the other support, e.g., out of a position in which the movable support is adjacent to the other support and in which it closes the opening in the machining table together with the other support. Thereby, a gap can be formed between the supports. Then workpiece parts, which have a greater width in the displacement direction than the sum of the widths of the two supports, can be moved into the discharge position. In this case, the movable support can be displaced until the opposing ends of the workpiece part rest only on the two supports and not on the machining table. As soon as the displaceable support has reached such a position, the supports can be accelerated out of the support position as described herein.

In another aspect, a method of moving a workpiece part, which has been completely cut out of a preferably plate-shaped workpiece, especially a metal sheet, from a support position, in which the workpiece part lies on the upper surface of a support located in a support position, into a discharge position located underneath the support includes accelerating the support, at least in the region of the workpiece part lying thereon, out of the support position in the gravitational direction with an acceleration which is greater than an acceleration of the workpiece part in the gravitational direction, and moving the accelerated support into an open position located outside the path of movement of the workpiece part at a speed such that the workpiece part attains the discharge position in free fall. The method can enable the workpiece part to be moved into the discharge position quickly and reliably.

The or, e.g., each support can be preferably lowered in the gravitational direction in a linear movement for acceleration out of the support position, wherein the linear movement can be effected over a distance of, e.g., at most 5 mm, in particular at most 2 mm. Owing to the linear movement, workpiece parts, which are arranged on the upper surface of the support in the vicinity of the rotation axis, can also be lifted from the upper surface of the support, which would require very high acceleration in the case of pure rotational movement.

In some embodiments, one, or, e.g., each support can be pivoted about a rotation axis preferably extending at right angles to the gravitational direction to accelerate the support at least within the region of the workpiece part lying thereon and/or to move the accelerated support into an open position located outside the path of movement of the workpiece part. Further, one can combine a linear movement, during which the workpiece part is lifted from the support, and a subsequent rotational movement for moving the support out of the path of movement of the workpiece part.

In addition, the aforementioned features and the features mentioned herein below can be employed individually or jointly in any combination.

DETAILED DESCRIPTION

FIG. 1shows a machine tool1, in particular, a laser punching press, with a conventional punching device3and a laser machining head4as tools for machining a workpiece2, e.g. a metal sheet. During machining, the workpiece2lies on a machining table5. With a conventional holding arrangement6with clamps7for securing the workpiece2, the workpiece2can be displaced relative to the fixed punching device3and the laser machining head4in an X direction that lies within the plane of the metal sheet, which defines an X-Y plane of an XYZ co-ordinate system as indicated inFIG. 1. By means of a conventional coordinate guide (not shown), the machining table5is mounted on a base8such that the workpiece2can be moved in a Y direction within the plane of the metal sheet by moving the machining table5and the holding arrangement6together relative to the base8.

Accordingly, the workpiece2can be displaced relative to the punching device3and the laser machining head4in the X and Y directions and respective region of the workpiece2can be moved into a spatially fixed machining region9of the punching device3or into a machining region11of the laser machining head4. The machining region11is confined by a substantially circular suction opening10in the machining table5. The suction opening10serves to remove, by suction, waste material and gases, which are produced during machining of the workpiece with the laser machining head4. An area of the workpiece table5in the X direction, on which the machining regions9,11are formed, is fixed and is not displaced in relation to the base8in the Y direction, so that the suction opening10is always positioned underneath the laser machining head4.

After a region of the workpiece2to be machined has been moved into the machining region11, the laser machining head4is activated to cut an, e.g., rectangular workpiece part12completely out of the workpiece2.

The cut out workpiece part12rests in the plane of the metal sheet on a first support13aand a second adjacent support13b, which are positioned in the plane of the metal sheet and are configured as flaps. The first support13ais arranged directly below the laser machining head4and includes the suction opening10that defines the machining region11.

To move the workpiece part12out of the plane of the metal sheet into a discharge position (not shown) located underneath the plane of the metal sheet, the supports13a,13bcan be pivoted about two parallel rotation axes15a,15bon opposite sides14a,14b. InFIG. 1, the rotation axes15a,15bare spaced apart by a spacing, which corresponds to twice the width (2b) of the two supports13a,13bin the Y direction. Workpiece parts with a greater dimension in the Y direction than that spacing cannot be moved into the discharge position when the supports13a,13bare configured as shown inFIG. 1.

To enable larger workpiece parts also to be moved into the discharge position, the second support13bis mounted to a displacement arrangement16that is configured as a displacement table and can be displaced together with the displacement arrangement in the Y direction within the plane of the metal sheet. The spacing between the two rotation axes15a,15bthereby increases in the Y direction, and an opening (not shown) is formed in the machining table5between the two supports13a,13b. The second support13bis displaced until the opposing ends of the workpiece part rest only on the upper surfaces of the two supports13a,13band not on the workpiece table5itself.

The movement of the workpiece part12from a process position P into a discharge position W lying there below will be further described in the following with reference toFIGS. 2a-c, which schematically show sequential steps of the movement of the supports13a,13bduring this process. The spacing between the first support13aand the second supports13bin the Y direction is as shown inFIG. 1. InFIG. 2a, the supports13a,13bare located in a support position S in the plane of the machining table5. InFIG. 2b, the supports13a,13bare in an intermediate position I and inFIG. 2c, the supports are in an open position O.

InFIG. 2a, the workpiece part12lies on upper surfaces of the supports13a,13b. To move the workpiece part12into the discharge position W in free fall, the two supports13a,13bare accelerated downwards in a linear manner from the support position S with an acceleration aAin the gravitational direction17, which corresponds to the negative Z direction. The acceleration aAis about three times the acceleration due to gravity aGthat acts on the workpiece part12. Owing to the linear movement of the supports13a,13bdownwards over a distance d of approximately 3 mm, the workpiece12is lifted from the supports13a,13b, as shown inFIG. 2b. The two supports13a,13bare subsequently pivoted about their respective rotation axes15a,15b, as indicated by arrows16inFIG. 2b, and are thereby moved into the open position O located outside the path of movement18of the workpiece part12, as shown inFIG. 2c. Thus, the workpiece part12can free-fall into its discharge position W from which the workpiece part12can subsequently be discharged from the machine tool1.

As an alternative to the above-described movement of the supports13a,13b, which is a combination of a linear movement and a pivoting movement, the same result can also be achieved by only pivoting the supports13a,13b. In this case, however, the acceleration, which is required to separate the workpiece part12from the supports13a,13bwithout it sliding along the supports13a,13b, is dependent upon the distance of the workpiece part12from the respective rotation axes15a,15b. The smaller the distance of the workpiece part12from the rotation axes15a,15b, the greater the acceleration must be during the pivoting movement.

As a further alternative to the sequence of movements described in connection withFIG. 2, the workpiece part12, which initially lies on the upper surface of the supports13a,13b, can be moved by means of a linear movement over a distance of e.g. a few millimeters into a position located underneath the plane of the metal sheet in order to prevent the workpiece part from catching on the remainder of the workpiece (not shown). The above-described sequence of movements can then be carried out starting from this lowered position. As an alternative to the pivoting movement of the supports13a,13b, the supports13a,13bcan also be moved out of the path of movement18of the workpiece part12in a different manner, e.g., in a linear movement at right angles to the gravitational direction17.

How the sequence of movements described inFIGS. 2a-ccan be implemented from a constructional point of view is described with reference toFIGS. 3a, bandFIG. 4, which each show detailed views of a lower part of the machine tool ofFIG. 1. To provide the movement of the supports, the machine tool1is provided with a motion unit, shown inFIG. 3a. The motion unit includes, an electric motor serving as a drive19which is motionally coupled via a toothed belt20to a threaded spindle22. The spindle22is guided in an overload-protected bearing21. The threaded spindle22of the motion unit has a spindle nut23, which can be moved in and counter to the gravitational direction17. The spindle nut23is fixed to a guide24. The guide24itself is guided in a linear manner within a longitudinal plate25and can be displaced in and counter to the gravitational direction17.

As shown inFIG. 3b, the guide24includes a guide rail27, which extends horizontally. The guide rail27guides two connecting pieces28a,28bto be linearly displaceable. The connecting pieces28a,28beach act upon one of the supports13a,13beccentrically to the rotation axes15a,15b. The connecting pieces28a,28bare rotatably mounted on the supports13a,13b, whereas they are non-rotatably guided along the guide rail27. If the drive19moves the spindle nut23downwards, the guide24is lowered and the connecting pieces28a,28bmove downwards as well guided by the guide rail27. During the downward movement, the connecting pieces28a,28bare simultaneously displaced horizontally along the guide rail27as a result of their non-rotatable mounting. As to the connecting pieces28a,28bact eccentrically to the rotation axes15a,15bonto the supports13a,13b, the supports13a,13bare pivoted downwards out of their horizontal position during this movement.

To provide in addition to the pivoting movement a linear movement as shown in the first part of the sequence of movements ofFIGS. 2a-c, the rotation axes15a,15bcan be moved in or counter to the gravitational direction17. This can be achieved by moving the connecting pieces28a,28bfurther upwards than would be necessary for a horizontal orientation of the supports13a,13b. Then, the supports13a,13bare pressed against a stop (not shown), which prevents an upwards pivoting movement of the supports13a,13bout of the horizontal orientation. During this process, a force is exerted on the supports13a,13band thus also on the bearings of the rotation axes15a,15b.

As shown inFIG. 3a, the rotation axis15ais rotatably mounted on a supporting plate29extending vertically, i.e., in the gravitational direction17. The supporting plate29is guided on a further plate30—likewise extending in the gravitational direction17—of a transverse frame (not shown). When applying a force counter to the gravitational direction17, the supporting plate29can be biased by a stop unit31, which includes a spring unit (not shown) acting as a shock absorber and a hydraulic piston (not shown). The force applied counter to the gravitational direction17through the connecting pieces28a,28bpushes the supporting plate29and the bearing of the rotation axis15aupwards against the spring or hydraulic force acting in the gravitational direction17, typically with a stroke of approximately 3-5 mm.

If the drive19moves the connecting pieces28a,28bdownwards, the rotation axes15a,15balso move downwards synchronously therewith as a result of the bias. Accordingly, the supports13a,13bexecute a linear movement parallel to the plane of the metal sheet over the distance of the bias. If the connecting pieces28a,28bare moved further downwards, the above-described pivoting movement of the supports13a,13bimmediately follows the linear movement. The speed of the pivoting movement is adapted to the preceding linear movement so that the workpiece part can no longer strike the supports13a,13bafter having been lifted thereof.

FIG. 4shows the supports13a,13bafter termination of the above-mentioned movement into the open position. The supports13a,13bhave been fully pivoted and form an angle of approximately 80° with the plane of the metal sheet. To discharge a workpiece part from the working region of the machine tool1after the free-falling movement as shown inFIGS. 2a-c, a movable slide32is mounted on the first connecting piece28a, as can also be seen inFIG. 3b. The parallel displacement of the connecting piece28amoves the movable slide32downwards. In the open position of the supports13a,13b, the movable slide32projects into the path of movement (not shown) of the workpiece part. In the open position of the supports13a,13b, a fixed slide33directly adjoins the movable slide32. In its discharge position, a free-falling workpiece part therefore strikes either the fixed slide33or the movable slide32and can be discharged from the working region of the machine tool1in a sliding movement.

The movable slide32, which is provided in addition to the fixed slide33, additionally can cover a suction tube34, which, in the support position S of the supports13a,13b, is in fluid connection with the suction opening10of the first support13a. As shown inFIG. 3a, the suction tube34is fixed to the spindle nut23and is moved downwards during the displacement of the latter in the gravitational direction17. An end piece35of the suction tube34is mounted to the first support13aand is pivoted therewith, as shown inFIG. 4. A beam dump (not shown) is provided at a lower end of the suction tube34to absorb the laser beam passing through the suction opening10during laser operation.

A light grid36detects when a workpiece part has attained the discharge position and is formed by a series of light barriers in a horizontal direction at the height of the transition between the fixed slide33and the movable slide32. The light barriers each comprise a light source37and an associated sensor38. The discharge position, at which the workpiece part strikes the slides32,33in free fall, depends on the dimensioning of the workpiece part. For example, the workpiece part can initially fully strike the movable slide32and pass the light grating36when it slides down onto the fixed slide33.

The supports13a,13bshould be moved back into the supporting position as soon as possible after the workpiece part has been detected in the discharge position to resume machining of the workpiece as quickly as possible. However, the arrangement of the light grid36underneath the movable slide32can prevent the support13afrom being pivoted upwards too soon and thereby possibly taking with it a workpiece part still partly lying thereon.

A number of embodiments of the invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. For example, the above-described sequence of movements can be employed not only for the removal of workpiece parts from the machining region11of the laser machining head4, but also for the removal of workpiece parts from the machining region9of the punching device3. Furthermore, removal in the above-described manner can also be applied in other machine tools. For example, in punching/bending machines, the workpiece parts, having been cut out, and/or processed further in a bending operation, can be moved from the process position into the discharge position.