Abstract:
There is provided a method and a device capable of holding a sheet-like workpiece without wrinkles. The sheet-like workpiece holding method has steps of mounting the sheet-like workpiece in a state in which almost no tensile force is applied thereon on a machining table, pressing out wrinkles of the sheet-like workpiece by lowering a pressing member whose surface facing to the workpiece protrudes in the shape of a convex lens toward the workpiece so that the workpiece is pressed against the machining table, retaining the sheet-like workpiece on the machining table by means of sunction while continuously pressing the sheet-like workpiece by the pressing member and releasing the pressing force of the pressing member while retaining the sheet-like workpiece.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to a method and a device for holding a sheet-like workpiece by rolling out the sheet-like workpiece wound in a roll to hold a part thereof on a flat table. The invention is suitably applicable to a laser machining apparatus for machining a flexible printed board for example.  
       BACKGROUND TECHNOLOGY  
       [0002]     As a machining apparatus for machining a sheet-like workpiece, there has been known a laser machining apparatus having, successively, an unwinding unit for unwinding a non-machined material-to-be-machined wound in a roll, a machining unit having a machining section (laser head) for drilling the material-to-be-machined unwound from the unwinding unit and a take-up unit for taking up the finished material in a roll as disclosed in Japanese Patent Laid-Open No. 2004-195510 for example. The laser machining apparatus also includes a machining table disposed so as to be movable relatively with respect to a main frame of the machining apparatus to move and position a plurality of blocks of the material to be machined existing in a longitudinal direction of the material sequentially to position for machining by the machining section, clamp means disposed in a body with the machining table and operates so as to clamp the material to be machined with respect to the machining table when the machining table moves from the position for starting machining by the machining section to position for ending the machining and so as to release the material to be machined from the machining table when the machining table returns to the machining starting position from the machining ending position and relative position fixing means that operates so as to fix relative position of the material to be machined to the machining apparatus in advance of the operation of the clamp means of releasing the material to be machined when the machining table reaches to the machining ending position and so as to release the fixed state of the relative position of the material to be machined to the machining apparatus after when the material to be machined is clamped by the clamp means when the machining table returns to the machining starting position.  
         [0003]     This technology makes it possible to prevent the position of a printed board, i.e., a sheet-like workpiece, from deviating from the laser head and hence to improve machining efficiency.  
         [0004]     It is noted that the sheet-like printed board is often positioned on the machining table while tensioning the printed board by applying a slight tensile force between a feed roll and a take-up roll and by fixing the printed board on the machining table by means of suction or fixtures such as a clamper.  
         [0005]     There has been also known a laser machining apparatus having at least a pair of clamps for holding both ends of a material to be machined and a tensioning unit for applying bias between the pair of clamps in a direction of relatively separating from each other to apply a tensile force to the material to be machined as disclosed in Japanese Patent Laid-Open No. 1998-296473 for example.  
         [0006]     Since this technology allows the material to be kept flat even if it is apt to curl, it allows machining accuracy to be improved.  
         [0007]     By the way, in drilling a printed board on which copper foil is provided by means of laser, etching is carried out before the drilling and a thickness of the printed board becomes uneven due to etching. Therefore, the printed board wound in a roll after etching causes wrinkles formed almost in parallel with a running direction the printed board.  
         [0008]     It is unable to smooth out the wrinkles formed almost in parallel with the running direction even if a tensile force is applied in the running direction of the printed board. Therefore, the printed board on which etching process has been carried out is held on the table while having the wrinkles.  
         [0009]     Although no hole can be machined, causing defective machining, at the wrinkled part because it is out of focus there in case of laser machining, no consideration has been given on the wrinkles running almost in parallel with the running direction of the sheet-like workpiece in the both documents of Japanese Patent Laid-Open Nos. 2004-195510 and 1998-296473.  
         [0010]     Accordingly, it is an object of the invention to provide a method and a device capable of holding a sheet-like workpiece on a table without wrinkles.  
         [0011]     This object may be achieved through the combination of features described in independent claims of the invention. Dependent claims thereof specify preferable embodiments of the invention.  
       SUMMARY OF THE INVENTION  
       [0012]     In order to solve the above-mentioned problem, according to the invention, there is provided a method for holding a sheet-like workpiece by rolling out the sheet-like workpiece wound in a roll so as to hold a part thereof on a flat table, having steps of mounting the sheet-like workpiece on the table (see  FIG. 3A ), pressing out wrinkles of the sheet-like workpiece by pressing the mounted sheet-like workpiece by a pressing member from a side (upper side) opposite from the table (see  FIG. 3B ), retaining the sheet-like workpiece on the table (by means of suction for example) while continuously pressing the sheet-like workpiece (see  FIG. 3C ) and releasing the pressing force of the pressing member while retaining the sheet-like workpiece.  
         [0013]     According to the invention, there is also provided a device for holding a sheet-like workpiece, having a flat table having retaining means (suction means for example) for retaining the sheet-like workpiece and a pressing member which is disposed so as to face to the table and which is capable of contacting with the table, wherein the device presses out wrinkles of the sheet-like workpiece by pressing the sheet-like workpiece by the pressing member from a side opposite from the table while mounting the sheet-like workpiece on the table and retains the sheet-like workpiece on the table by the retaining means while pressing the sheet-like workpiece.  
         [0014]     The invention allows the sheet-like workpiece to be fixed on the table without wrinkles, so that it allows the machining quality to be improved.  
         [0015]     It is noted that the summary of the invention described above does not necessarily describe all necessary features of the invention. The invention may also be a sub-combination of the features described above.  
       BRIEF DESCRITION OF THE DRAWINGS  
       [0016]      FIG. 1  is a front partially section view of a laser machining apparatus to which the invention is applied.  
         [0017]      FIG. 2  is an enlarged view of a part A in FIG.  
         [0018]      FIGS. 3A through 3K  are drawings for explaining operations of the laser machining apparatus to which the invention is applied and show different states thereof, respectively.  
         [0019]      FIG. 4  is a drawing showing directions of force of a pressing member acting on a workpiece.  
         [0020]      FIGS. 5A and 5B  are drawings showing directions of force of the pressing member on a workpiece, wherein  FIGS. 5A and 5B  show different embodiments, respectively. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0021]     The invention will now be described based on preferred embodiments shown in the drawings, which do not intend to limit the scope of the invention, but exemplify the invention. All of the features and the combinations thereof described in the embodiments are not necessarily essential to the invention.  
         [0022]      FIG. 1  is a front partially section view of a laser machining apparatus  50  to which the invention is applied,  FIG. 2  is an enlarged view of a part A in  FIG. 1  and  FIGS. 3A through 3K  are drawings for explaining operations of the laser machining apparatus  50 .  
         [0023]     In the laser machining apparatus  50  of the invention, a gate-like column  30  is fixedly installed on a bed  1 . Disposed on the column  30  are a laser oscillator  31 , a plurality of mirrors  32  (two in the figure), a pair of optical mirrors  33  and an fè lens  34 .  
         [0024]     A linear guide  2  is disposed on the upper face of the bed  1 , so that an X table  3  is movable on the bed  1  in the X direction. A linear guide  4  is disposed on the upper face of the X table  3 , so that a Y table (mobile table)  5  is movable on the X table  3  in a Y direction. Accordingly, from the configuration described above, the Y table  5  is movable in the X and Y directions with respect to the bed  1 .  
         [0025]     Disposed on the upper face of the Y table  5  are a machining table  6  and a reel holder  10  as shown in  FIG. 2 . A channel  6   m  having a transverse width wider than a width of a sheet-like workpiece (referred to simply as a workpiece hereinafter) w such as a flexible printed board is formed on a lower face of the machining table  6  in the X direction. A plurality of holes connected with a hollow section not shown within the machining table  6  is formed on the upper face of the machining table  6 . The hollow section not shown within the machining table  6  is connected with a vacuum source not shown. These components compose retaining means. The reel holder  10  is provided with a feed reel  11 , a take-up reel  12 , guide rollers  13 ,  14  and  15 , clampers  16  and  17 , a turning roller  18  and a workpiece conveying unit (moving means)  20 .  
         [0026]     The feed roll  40  in which non-finished workpiece w is wound in a roll is held by the feed reel  11 . The feed reel  11  is held by the reel holder  10  and is rotatable by a motor not shown. A bottom  11   b  of the feed reel  11  is positioned under a top  13   t  of the guide roller  13  adjacent thereto. Accordingly, the feed reel can feed the workpiece w when driven by the motor not shown (feed side roll holder).  
         [0027]     A take-up roll  41  is what the finished workpiece w is taken up in a roll. The take-up roll  41  is held by the take-up reel  12 . The take-up reel  12  is held by the reel holder  10  and is rotatable by a motor not shown. The take-up reel  12  is disposed at the position where a bottom  41   b  of the take-up roll  41  is higher than a bottom  14   b  of the guide roller  14  adjacent to the take-up roll  41 . Accordingly, the take-up reel  12  can take up the workpiece w when driven by the motor not shown (take-up side roll holder).  
         [0028]     The reel holder  10  supports the rotatable guide roller  13  so that a top  13   t  thereof is higher than a surface (upper face) of the machining table  6 . The reel holder  10  also supports the rotatable guide rollers  14  and  15  so that their bottoms  14   b  and  15   b  are lower than a bottom face of the channel  6   m.    
         [0029]     The clampers  16  and  17  are composed of receptors  16   u  and  17   u  and pressers  16   p  and  17   p  disposed so as to face to the receptors  16   u  and  17   u  and are movable respectively in the Z direction (in the vertical direction in the figure) by means not shown, except of the receptor  17   u . A lowering end of the receptor  16   u  is set at its standby position and at this time, its upper face is located at position lower than the surface of the machining table  6  and when the receptor  16   u  is located at its rising end, the upper face is located at position on the same height with the top  13   t  of the guide roller  13 , i.e., above the surface of the machining table  6 . Still more, a lowering end of the presser  16   p  is set at position slightly under the upper face of the receptor  16   u  in the standby position so that the lower face of the presser  16   p  can press the upper face of the receptor  16   u . A lowering end of the presser  17   p  is also set at position slightly under the upper face of the receptor  17   u  so that the lower face of the presser  17   p  can press the upper face of the receptor  17   u . The reel holder  10  supports the rotatable turning roller  18  so that a top  18   t  thereof is set at position on the same height with the top  13   t  of the guide roller  13 .  
         [0030]     The workpiece conveying unit  20  may be freely moved and positioned in the X direction with respect to the reel holder  10  by means of a motor and a guide rail mechanism not shown. The workpiece conveying unit  20  supports a clamper  21 . The clamper  21  is composed of a presser  21   p  and a receptor  21   u  movable in the vertical direction. Standby position of the receptor  21   u  is set at position whose upper face is lower than the upper face of the machining table  6  as shown by a solid line in  FIG. 2  and its rising end is set at position on the same height with the top  13   t  of the guide roller  13  and the top  18   t  of the turning roller  18 . Still more, standby position of the presser  21   p  is set at position where a lower face thereof is higher than the top  13   t  of the guide roller  13  and the top  18   t  of the turning roller  18  as shown by a solid line in the figure and a lowering end thereof is set at position slightly below the upper face of the receptor  21   u  located at its rising end so that the lower face of the presser  21   p  can press the upper face of the receptor  21   u  located at its rising end. It is noted that standby position of the workpiece conveying unit  20  in the X direction is set at a movable left end shown by solid lines in the figure and its movable right end is position shown by dot lines in the figure.  
         [0031]     As shown in  FIG. 1 , a pressing plate  60  is disposed in the column  30  so as to face to the Y table  5 . A pressing member  61  made from an elastic member is fixed under the pressing plate  60 . A surface (facing to the Y table  5 ) of the pressing member  61  is a curved surface convex to the machining table  6 , or more specifically, is a curved surface formed in the shape of a convex lens and having an apex at the center of the X and Y directions of the pressing plate  60 . The pressing plate  60  may be moved and positioned in the vertical (Z) direction by a lift  62  held in the column  30 .  
         [0032]     Next, an operation of the laser machining apparatus  50  will be explained along the drawings. It is supposed that a non-finished workpiece w held in the feed roll  40  has wrinkles in the running direction (X direction)  
         [0033]     At first, arrangements for this operation will be explained. That is, while opening all of the clamps  16 ,  17  and  21  in advance, i.e., while positioning the receptors  16   u  and  21   u  at their standby positions and the pressers  16   p ,  17   p  and  21   p  at their rising ends, respectively, the feed roll  40  is put on the feed reel  11 , the workpiece w is wound around the turning roller  18  and is passed through the channel  6   m  of the machining table  6  and its end is fixed to the take-up reel  12  (the take-up roll  41 ).  
         [0034]     Next, the presser  16   p  is lowered while applying clockwise torque in the figure slightly to the feed reel  11  and the take-up reel  12  to hold the workpiece w by the clamper  16  while smoothing out wrinkles in the direction orthogonal to the running direction. Still more, the presser  17   p  is lowered so that the clamper  17  holds the workpiece w. Then, the workpiece w is fixed on the upper face of the machining table  6  in a state in which tensile force is applied slightly thereon in the running direction as shown in  FIG. 3A .  
         [0035]     Although the wrinkles in a part of the workpiece w clamped by the clampers  16  and  17  are smoothed out as the clampers  16  and  17  hold the workpiece w at this time, the wrinkles around the center of the machining table  6  remain without being smoothed out.  
         [0036]     Next, after positioning the center of the machining table  6  to the center of the pressing member  61  by moving the Y table  5 , the pressing plate  60  is lowered to a point where the surface of the pressing member  61  becomes almost flat as shown in  FIG. 3B . It is noted that the whole area to be machined of the workpiece w contacts with and is pressed by the pressing member  61  at this time. After when the pressing member  61  contacts with the workpiece w, a contact area of the pressing member  61  with the workpiece w expands concentrically as indicated by arrows in  FIG. 4  and the wrinkles formed on the workpiece w are pressed out.  
         [0037]     Next, a vacuum source not shown is put into operation while lowering the pressing plate  60  so that the workpiece w is sucked to the surface of the machining table  6  as shown in  FIG. 3C . As a result, the workpiece w is fixed on the surface of the machining table  6  without wrinkles.  
         [0038]     After completing the fixation of the workpiece w described above, machining is carried out. That is, the machining table  6  is moved to position an area to be machined with respect to the fè lens  34 , the laser oscillator  31  is put into operation and a laser beam outputted from the laser oscillator  31  is guided to the optical mirror  33  via the mirrors  32 . Then, the laser beam is positioned by the optical mirror  33  and is caused to be incident on the workpiece w by the fè lens  34  while vertically setting an optical axis of the laser beam to machine the workpiece w. After ending the machining of the machining area determined by the fè lens  34 , the X table  3  or the Y table  5  is moved to machine a next machining area.  
         [0039]     Next, a step for moving the workpiece after ending machining will be explained. After ending machining, the vacuum source not shown is turned off to stop the operation of the machining table  6  of sucking the workpiece w and the presser  16   p  is raised. Then, the clamper  21  is put into operation as shown in  FIG. 3D . That is, after raising the receptor  21   u , the presser  21   p  is lowered so as to hold the workpiece w by the presser  21   p  and the receptor  21   u.    
         [0040]     Next, the presser  17   p  is raised as shown in  FIG. 3E . As a result, the workpiece w is positioned at height of the top  13   t  of the guide roller  13  and the top  18   t  of the turning roller  18 .  
         [0041]     In this state, the workpiece conveying unit  20  is moved to the right in the figure by a desirable distance as shown in  FIG. 3F . It is noted that at this time, the workpiece w whose machining has been finished is taken up by the take-up reel  12  while feeding the workpiece w by the feed reel  11 .  
         [0042]     Next, after moving the receptor  16   u  to its raising end, the presser  16   p  is lowered as shown in  FIG. 3G  to hold the workpiece w by the clamper  16 .  
         [0043]     Next, the clamper  21  is released. At this time, the presser  21   p  is moved to its raising end and the receptor  21   u  is moved to position where its upper face does not contact with the workpiece w and where it does not contact with the upper face of the machining table  6 , respectively. Then, the workpiece conveying unit  20 , i.e., the clamper  21 , is returned to its standby position as shown in  FIG. 3H .  
         [0044]     Next, after positioning the receptor  21   u  to its standby position as shown in  FIG. 3I , the presser  17   p  is lowered to hold the workpiece w by the clamper  17  as shown in  FIG. 3J . Then, the clamper  16  is released as shown in  FIG. 3K . Then, after positioning the receptor  16   u  to its standby position, the presser  16   p  is lowered to hold the workpiece w by the clamper  16  (see  FIG. 3A ). These steps are repeatedly carried out thereafter.  
         [0045]     During the steps described above and during machining, the feed reel  11  and the take-up reel  12  are driven with a certain range of torque that will give no adverse effect on the workpiece w to apply the tensile force to the workpiece w so that the workpiece w does not sag. It is noted that tensile force may be applied to the workpiece w so that the workpiece w does not sag by biasing the rollers  13  and  14 , the turning roller  18  and others in predetermined directions by springs or the like.  
         [0046]     As described above, because the laser machining apparatus  50  adopting the inventive sheet-like workpiece holding method allows the workpiece w to be machined without wrinkles, machining may be carried out in high quality.  
         [0047]     Still more, according to the present embodiment, because the feed reel and the take-up reel are disposed on one side on the machining table  6 , no space for forming a free loop of the sheet-like workpiece is required and an installation area of the whole laser machining apparatus  50  may be reduced. Further, because this configuration requires fewer components, the control can be made readily.  
         [0048]     Further, because the feed reel and the take-up reel are disposed on one side on the machining table  6 , the installation area of the whole laser machining apparatus  50  may be reduced as compared to a case of disposing them on the both sides of the machining table  6 .  
         [0049]     Still more, the invention allows the wrinkles to be pressed out even if the wrinkles run in the direction other than the running direction of the workpiece w. It is noted that although the surface of the pressing member  61  is formed into the shape of a convex lens so as to have its apex at the center of the X and Y directions of the pressing plate in the present embodiment, it may be a cylindrical face whose axis is disposed in parallel with the running direction (X direction). Thereby, because a contact area of the pressing member  61  with the workpiece w expands gradually in a width direction as shown in  FIG. 5A , the wrinkles caused in the workpiece w may be pressed out.  
         [0050]     The wrinkles of the workpiece w may be also pressed out in the same manner with the case described above by disposing the axis of the cylindrical face orthogonally or obliquely to the running direction as shown in  FIG. 5B .  
         [0051]     It is noted that the shape of the surface of the pressing member  61  may be any shape as long as it can increase its contact area with the workpiece w gradually from the center part to the peripheral part, such as a part of an ellipsoid.  
         [0052]     Still more, the pressing member  61  may be made from a solid elastic member or may have a space in which a fluid is filled. The pressing member  61  may be also a porous elastic member, e.g., sponge.  
         [0053]     When the pressing member  61  is made from sponge, the pressing member  61  may be separated readily from the workpiece w after sucking the workpiece w by the Y table  5  in the step in  FIG. 3C  even if through holes are formed in the workpiece w.  
         [0054]     An adhesive layer may be provided on the surface of the pressing member  61  to provide a function of removing dust on the surface of the workpiece w.  
         [0055]     The invention is applicable not only to the case of machining printed boards but also to a case of machining other sheet-like workpieces.  
         [0056]     Although the invention has been described by way of the exemplary embodiments, it should be understood that those skilled in the art might make many changes and substitutions without departing from the spirit and scope of the invention. It is obvious from the definition of the appended claims that the embodiments with such modifications also belong to the scope of the invention.