Abstract:
In a device for separating a longitudinally-extended cylindrical workpiece, which has a diameter in the sub-millimeter range, into individual segments, the workpiece is guided in a clamping device. The clamping device includes a first and a second clamping jaw and a feed opening for the workpiece. The feed opening is fitted between the clamping jaws on the side facing the other clamping jaw and a longitudinal groove which defines a direction of advancement of the workpiece for receiving and guiding the workpiece between the clamping jaws. The clamping device has a passage for a laser beam and a cutting gas, which passage defines a working zone, disrupts the longitudinal groove and runs parallel thereto. A cutter head is arranged in the working zone and has an outlet opening for the laser beam and the cutting gas, which outlet opening is aligned with the passage.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This is a continuation application, under 35 U.S.C. §120, of copending international application No. PCT/EP2013/060143, filed May 16, 2013, which designated the United States; this application also claims the priority, under 35 U.S.C. §119, of German patent applications No. DE 10 2012 211 206.5, filed Jun. 28, 2012 and DE 10 2012 212 718.6, filed Jul. 19, 2012; the prior applications are herewith incorporated by reference in their entireties. 
     
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
       [0002]    The invention relates to a device and a method for separating a longitudinally-extended cylindrical workpiece having a diameter in the sub-millimeter range into individual portions. 
         [0003]    In particular in the manufacture of vessel supports, or stents, used in medicine, structural elements in the form of thin tubes having a diameter in the sub-millimeter range, for example between 100 and 300 μm, and a length in the millimeter range, which are precision-manufactured in a reproducible manner and the production of which is associated with significant technical issues, are required. For such structural elements a thin cylindrical workpiece, typically a hollow-cylindrical tube which is wound up on a supply roll and from which the individual structural elements have to be severed after prior additional processing, serves in the form of semi-finished product as the raw material. A particular production issue here is in particular the severing operation in which the portions forming the individual structural elements are severed from the optionally pre-processed workpiece. 
         [0004]    A device for separating a hollow-cylindrical workpiece used in the manufacture of a stent into individual portions by a laser beam is known from published, non-prosecuted German patent application DE 10 2007 018 537 A1, for example, wherein the workpiece is guided in a guide body by way of a clamping force and wherein a free end of the workpiece which projects beyond this guide body is severed by the laser beam. Devices for manufacturing stents, in which a hollow-cylindrical semi-finished product is mounted in clamping devices for processing by a laser beam, are moreover disclosed in published, non-prosecuted German patent application DE 10 2008 011 232 A1 and in U.S. patent publication No. 2003/0234242 A1. 
       SUMMARY OF THE INVENTION 
       [0005]    The invention is now based on the object of stating a device with which it is possible to economically manufacture structural elements of this type in large numbers. The invention is moreover based on the object of stating a method which is suited to the manufacturing of such structural elements. 
         [0006]    With the foregoing and other objects in view there is provided, in accordance with the invention, a device for separating a longitudinally-extended cylindrical workpiece having a diameter in the sub-millimeter range into individual portions. The device contains a clamping device having at least one first and one second clamping jaw and an insertion opening for the workpiece. The workpiece is introduced in at least one of the clamping jaws on the side which faces the other clamping jaw. The clamping jaws have a longitudinal groove, which defines an indexing direction of the workpiece, for receiving and guiding the workpiece between the clamping jaws. The clamping device include an aperture for a laser beam and a cutting gas, which defines an operating zone and interrupts the longitudinal groove and runs transversely thereto. A cutting head is provided and has an exit opening for a laser beam and a cutting gas. The exit opening is aligned with the aperture and is disposed in the operating zone. 
         [0007]    On account of the insertion opening which is located in the first and/or second clamping jaw, insertion of the workpiece into the longitudinal groove which is introduced into the first and/or second clamping jaw on that side which is in each case opposite to the opposing clamping jaw is facilitated. 
         [0008]    Since processing of the workpiece is performed in an operating zone which, during processing of the workpiece by way of the laser beam and during impingement with the cutting gas, enables mounting of the workpiece on both sides of the aperture, precise processing of the workpiece, for example introduction of longitudinal slots, and also precise severing of small portions are both possible. 
         [0009]    Moreover, when the aperture is simultaneously provided as the first outlet opening for the portions which have been severed from the workpiece by the laser beam and is connectable to a first receiving container by way of a flexible hose, secure and controlled handling of the severed short portions is ensured. 
         [0010]    With respect to the method for separating a longitudinally-extended cylindrical workpiece into individual portions, the method includes the following steps: 
         [0011]    a) inserting the workpiece into the insertion opening of the clamping device, 
         [0012]    b) indexing the workpiece until it bridges the aperture, 
         [0013]    c) performing a severance cut by a laser beam within the aperture, and 
         [0014]    d) drifting out the severed portion through an outlet opening which is aligned with the aperture, and onward conveying of the portion by the cutting gas through a flexible hose into a first collection container. 
         [0015]    Since the workpiece is mounted on both sides of the aperture, precise processing and precise severing are both possible. Targeted drifting-out of the severed portion through the outlet opening and onward conveying of the severed portions by the cutting gas to a receiving container is also possible when the length of portion created hereby marginally exceeds the usable width of the aperture, since the portions tip into the aperture on account of the pressure exerted by the cutting gas. 
         [0016]    Other features which are considered as characteristic for the invention are set forth in the appended claims. 
         [0017]    Although the invention is illustrated and described herein as embodied in a device and a method for separating a longitudinally-extended cylindrical workpiece, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims. 
         [0018]    The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
         [0019]      FIG. 1  is an illustration of a device for separating a longitudinally-extended cylindrical workpiece according to the invention; 
           [0020]      FIG. 2  is a diagrammatic, perspective view of components which serve as clamping bodies of a clamping device used in the device; 
           [0021]      FIG. 3  is a longitudinal section view showing the clamping bodies illustrated in  FIG. 2 ; and 
           [0022]      FIG. 4  is an enlarged longitudinal section view of the clamping bodies in a region of an aperture which is located in the clamping device. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0023]    Referring now to the figures of the drawings in detail and first, particularly to  FIG. 1  thereof, there is shown a device having a cutting head  2  in which a laser beam generated by a non-illustrated laser-beam source is focused for cutting a workpiece  36  which is mounted in a clamping device  4 . A cutting gas SG, with which the non-illustrated workpiece is impinged during cutting, is additionally supplied to the cutting head  2 . The clamping device  4  has a first and a second clamping jaw  6  or  7 , respectively, between which the thin cylindrical workpiece having an outer diameter in the sub-millimeter range, in particular a circular tube, composed of plastic or of a precious metal, having an outer diameter between 100 μm and 1000 μm, is received and guided. A first clamping body  8  is inserted into the first clamping jaw  6 , and a second clamping body  9  is inserted into the second clamping jaw  7 , which fixate or clamp the workpiece during processing in such a manner that said workpiece can still be axially displaced and rotated during processing. 
         [0024]    In  FIG. 1 , the device is illustrated in a plan view onto that side of the clamping device  4  on which the workpiece is introduced through an insertion opening  10  between the first and second clamping jaws  6 ,  7 , or, respectively, between the first and second clamping bodies  8  or  9 , respectively, which are inserted into the first or second, respectively, clamping jaw  6  or  7 , respectively. 
         [0025]    The clamping device  4  is mounted in a frame  12 , whereby in the illustrated exemplary embodiment the first clamping jaw  6  is rigidly mounted in the frame  12  and the second clamping jaw  7  is mounted in the frame  12  so as to be displaceable in the direction of double arrows  14 , such that the second clamping jaw  7  can be closed toward the first clamping jaw  6 . A pretensioned spring  16 , in the example a helical spring which serves as a pull-spring, is disposed between the clamping jaws  6 ,  7 , the pretensioning and accordingly the clamping force F 1  acting between the clamping bodies  8 ,  9  of the spring  16  being adjustable. In the illustrated example, the spring  16  is fixated at one of its ends on a flange  18  of a mandrel  20  which serves for axially guiding the spring  16 . An opening, through which a rigid spacing element  21  which is connected to the other end of the spring  16  in a force-fitting manner is guided, is located in the second clamping jaw  7 . A sleeve  26 , which is provided with a thread and two longitudinal slots  24  which lie opposite one another, is disposed below the opening, onto which sleeve  26  a knurled nut  28  is screwed, a retaining pin  29  which is disposed on the spacing element  21  and protrudes through the longitudinal slots  24  engaging on the lower side of which knurled nut  28 , such that a rough adjustment of pretensioning is enabled with the aid of the latter. For the fine adjustment of pretensioning, the flange  18  is connected to a micrometer drive  30  and can be axially adjusted by way thereof, such that a fine adjustment of the clamping force F 1  is enabled. 
         [0026]    A lifting cylinder  31 , pneumatically actuatable with pressure gas DG, by way of which it is possible to exert a counterforce F 2  which acts counter to the clamping force F 1  in order to facilitate insertion of the wire-type workpiece between the first and second clamping bodies  8 ,  9  is disposed so as to be parallel to the spring  16  between the clamping jaws  6 ,  7 . 
         [0027]      FIG. 2  shows the first and second clamping bodies  8 ,  9  ( FIG. 1 ) which are in each case disposed in the first and second clamping jaws  6 ,  7 , in a perspective illustration. It may be derived from  FIG. 2  that the first clamping body  8  is formed by a strip which, on a narrow side which extends in a longitudinal direction, displays a cutting edge which in the cross section is V-shaped and by way of which the strip can be introduced into a longitudinal groove  32  which is located in the second clamping body  9  and which, in the cross section, is likewise V-shaped and which extends across the entire length of the second clamping body  9 . The cutting edge, on its end, is flattened and displays a width which approximately corresponds to the diameter of the workpiece  36 . 
         [0028]    The strip, on its end which faces an insertion opening  10 , is provided with an insertion ramp  34 , such that the insertion opening  10 , on account of a recess formed the insertion ramp  34  on the end face together with the longitudinal groove  32  which extends in the second clamping body  9  up to the end face, is enlarged, facilitating insertion of the thin cylindrical workpiece  36  into the longitudinal groove  32 . 
         [0029]    The workpiece  36  is fed to the first and second clamping bodies  8 ,  9  by a linear and rotary drive  40 , by way of which the workpiece  36  can be moved to and fro along its longitudinal axis in the direction of double arrow  42 , or can be rotated about its longitudinal axis in the direction of double arrow  44 , respectively. 
         [0030]    The first and second clamping bodies  8 ,  9  define a funnel-shaped operating zone  46 , within which the workpiece  36  can be separated into individual portions by a static laser beam L while a cutting gas SG is simultaneously supplied. Additionally, a plurality of cuts or longitudinal slots which are distributed on the circumference may moreover be introduced into the workpiece  36  before it is separated into individual portions. During processing with the laser beam L, the workpiece  36  is rotated about its longitudinal axis during severing. Alternatively thereto, it is also possible for the severance cut to be performed by a movement of the laser beam L which is transverse to the longitudinal axis of the workpiece  36 . Longitudinal slots which may be optionally required are introduced by axial displacement of the workpiece  36  prior to severing. 
         [0031]    The first and second clamping jaws  6 ,  7 , or the first or second clamping body  8 ,  9 , respectively, which are inserted there into, are configured in such a manner that, when viewed in the indexing direction, they exert a clamping force on the workpiece  36  only up to an aperture  68  ( FIG. 3 ) which is formed in the operating zone  46  for the laser beam  2  and the cutting gas SG. 
         [0032]    Moreover, a first and second outlet opening  48  or  50 , respectively, for the severed portions, which are in each case connected by way of a flexible hose  52  to a first or second, respectively, receiving container  54 ,  56 , are located on the second clamping body  9  in the region of the operating zone  46 . In this way, the severed portions are conveyed away from the operating zone  46  in a controlled manner. The hoses  52  are preferably composed of a metallic, tightly wound metal wire, in order to prevent an electrostatic charge and adhesion of the portions on the inner walls of the hoses  52  in particular when conveying portions composed of plastic. 
         [0033]    A counter bearing  60  which displays a funnel-shaped recess  62  which tapers in a conical manner and forms half of a cone, is disposed opposite the strip on the second clamping body  9 , so as to be able to position a likewise conically shaped cutting head  2  above the workpiece  36  at a spacing of only a few tenths of a millimeter between the exit opening and the workpiece  36 . For this reason, an end side  64  of the first clamping body  8  which faces toward the operating zone is also shaped in an oblique manner. 
         [0034]    It may now be derived from  FIG. 3  that the oblique end side  64  and the funnel-shaped recess  62 , which is located in the counter bearing  60 , align with a sequential bore  66  which is located in the second clamping body  9  and which forms the aperture  68  for the laser beam and the cutting gas in the clamping device  4 . Accordingly, the counter bearing  60  is located beside the aperture  68 , adjacent thereto on the side thereof which faces away from the insertion opening  10 , and covers the longitudinal groove  32  which is located in the clamping body  9 . Accordingly, the aperture  68  runs in a transverse manner to the longitudinal groove  32 , interrupts the latter and is aligned with the exit opening  48 . 
         [0035]    The aperture  68  which is located in the operating zone  46  is illustrated in an enlarged manner in  FIG. 4 . In  FIG. 4  the cutting head  2  which is inserted into the funnel-shaped operating zone  46  is moreover drawn using dashed lines, the exit opening  69  of which cutting head  2 , through which the laser beam L and the cutting gas SG exit, is aligned with the aperture  68 , whereby the central axis  70  of the cutting head  2  and the central axis  72  of the aperture  68  coincide. 
         [0036]      FIG. 4  shows a situation in which the workpiece  36  has been indexed so far that, with its free end, it protrudes into the longitudinal groove  32 , which is located below the counter bearing  60 , and bridges the aperture  68 . The diameter D of the workpiece  36  is smaller than a depth T of the longitudinal groove  32 , such that a narrow gap s exists between the counter bearing  60  which is disposed on the second clamping body  9  and the workpiece  36 . 
         [0037]    Since during separating or processing the workpiece  36  bridges the aperture  68  and is not only fixated on account of the clamping force which acts between the first and second clamping bodies  8 ,  9 , but moreover is supported at the free end by the second clamping body  9 , deformation or sagging, respectively, of the workpiece  36  during processing by the laser beam is limited, such that the severance cut and also the longitudinal cuts can both be performed with high precision. 
         [0038]    A severed portion  74  is automatically drifted downward out to the first outlet opening  48  ( FIG. 2  and  FIG. 3 ) by the cutting gas SG which flows into the aperture  68 , and is fed through the hose  52  to the first receiving container  54  ( FIG. 2 ). The counter bearing  60  which is located beside the operating zone  46  or beside the aperture  68 , respectively, serves for reliably conveying comparatively long portions, which cannot be drifted out through the aperture  68 , to the second exit opening  50 , in order to feed the portions to the second receiving container  56 . On account of the counter bearing  60  it is prevented that these comparatively long portions are blown away in an uncontrolled manner under the influence of the cutting gas SG. Where only short portions  74  are produced, the counter bearing  60  may also be dispensed with in principle. 
         [0039]    In the exemplary embodiment, tubular portions  70 , made of platinum Pt, having an outer diameter of 163 μm and a length of about 1000 μm, which are provided with a longitudinal slot on the circumference which extends across the entire length of the portion  70 , are produced.