Abstract:
Method and apparatus for making a rotary die blade from a straight blade blank to be conformable to the contour of the rotary die block include inserting a blade blank between a first press face of a first presser and a second press face of a second presser; and compressing the blade blank by urging either of the first press face or the second press face to the other, thereby elongating the blade blank along its length; wherein the compressive force is differentiated such that a stronger compressive force is applied to the peripheral portion of the blade blank than the inner portion thereof.

Description:
TECHNICAL FIELD 
   The present invention relates to method and apparatus for making a rotary die blade from a straight blade blank, and more particularly, method and apparatus for making a rotary die blade from a straight blade blank conformable to the contour of the die block. 
   BACKGROUND ART 
   A rotary die equipped with a blade is used for perforating a work, such as paper, to facilitate separation, or for punching or stamping.  FIGS. 14 and 15  show a rotary die block  100  and a rotary anvil  200  used in association with the rotary die block  100 . The die blade  1  has a cutting edge  12  which is curved along the contour of the die block, and projected beyond its periphery so as to penetrate a work (W) such as paper or metal sheet. 
   By referring to  FIGS. 14 and 15 , the conventional rotary die unit will be described: 
   A work (W) such as paper or metal sheet is passed between the rotary die  100  equipped with a die blade  1  and the rotary anvil  200  in the direction (F) indicated by the arrow. While passing therebetween, the work (W) is subjected to perforating or slitting or stamping operations as desired by the blade  1 . The rotary anvil  200  has two kinds; one having a hard surface as of iron, and the other having a soft surface made as of rubber, depending upon the nature of the work (W). 
   The blade  1  fixed to the rotary die block  100  has two kinds; one is obtained by curving a straight strip shown in  FIG. 16 , and shaping it on the user&#39;s side as shown in  FIG. 17 , and the other is obtained by procuring a previously curved blade commercially available. In the latter case, it will be very handy if the obtained blade has a curvature as desired, and in the former case, the blade can be curved on the user&#39;s side to a desired curvature, where, as shown in  FIG. 17 , three rollers  301 ,  302  and  303  are employed with one being inside and the other two outside. Each of the rollers  302  and  303  is provided with a groove on its rim so as to support the edge  12  in a non-contact manner. This method is disclosed in Japanese Patent Publication No. 46 (1971)-18352. 
   The problem arises from the latter case shown in  FIG. 19 , in the form of the betrayal of the expectations of handiness and readiness because of the difficulty in selecting a curvature agreeable to the desired value. The problem of the former case shown in  FIG. 17  is that parts (A) are likely to remain unprocessed because of the structural limitation inherent in the illustrated type of machine. These unprocessed parts (A) must be removed by an extra process, thereby increasing the production cost. 
   Therefore, an object of the present invention is to provide a method and apparatus for obtaining rotary die blades conformable to the contour of the die block throughou its full length. 
   Another object of the present invention is to provide a method and apparatus for variously shaping the edge of the die blade as the user desires. 
   A further object of the present invention is to provide a method and apparatus for ensuring the conformity of the die blade to the contour of the rotary die block without requiring a special skill. 
   A still further object of the present invention is to provide a method and apparatus for ensuring the conformity of the die blade to the contour of the rotary die block under a computer control. 
   SUMMARY OF THE INVENTION 
   According to one aspect of the present invention, there is provided a method for making a rotary die blade from a straight blade blank, includes inserting a blade blank between two pressers, that is, a first presser having a first press face, and a second presser having a second press face, respectively; and compressing the blade blank by urging either of the first press face or the second press face to the other, thereby elongating the blade blank along its length under compression, wherein a stronger compressive force is applied to the peripheral portion of the blade blank than to the inner portion thereof. 
   In an alternative embodiment the blade blank is provided with a plurality of slits produced at intervals, wherein the distance between the bottom of each slit and the outside rim of the blade blank is not larger than one half of the full width of the blade blank. 
   According to another aspect of the present invention, there is provided an apparatus for making a rotary die blade from a straight blade blank, includes a first presser having a first press face and a second presser having a second press face; a first carrier carrying the first presser; a second carrier carrying the second presser; and a housing for accommodating the pressers and the carriers of the pressers; wherein either of the first carrier or the second is movable to and from the other carrier, thereby bringing the press faces into contact with each other so as to compress the blade blank. 
   In an alternative embodiment, each of the first and second press faces is inclined so as to form an upwardly diverged space between the two press faces, thereby differentiating the compressive force between a lower section and an upper section of the diverged space when the two press faces are brought into contact with each other. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a diagrammatic perspective view showing an apparatus embodying the present invention; 
       FIG. 2  is a diagrammatic side view to show the internal structure of the apparatus shown in  FIG. 1 ; 
       FIG. 3  is an explanatory view showing the positional relationship between a blade blank and the presser; 
       FIG. 4A  is a diagrammatic sectional view taken along IV—IV line in  FIG. 3  where a blade blank is inserted between the two pressers, and  FIG. 4B  is a diagrammatic sectional view taken along IV—IV in  FIG. 3  where the two pressers are brought into contact with each other, with the blade blank therebetween; 
       FIG. 5  is an explanatory view illustrating the process of applying compression and elongation to the blade blank; 
       FIG. 6  is a diagrammatic view showing an advantageous case where a presser adapted for shaping the blade blank has a desired shape; 
       FIG. 7  a diagrammatic view explaining another advantageous case where a presser has a desired shape; 
       FIG. 8  is a diagrammatic view showing the shapes of the press faces; 
       FIG. 9  is a diagrammatic plan view showing a blade blank bent in a direction of thickness; 
       FIG. 10  is a diagrammatic plan view of another type of blade blank; 
       FIG. 11  is a diagrammatic plan view of a pre-curved blade blank; 
       FIG. 12  is a diagrammatic perspective view of a blade blank in the process of being curved; 
       FIG. 13  a diagrammatic perspective view of a blade blank which has been curved; 
       FIG. 14  is a diagrammatic perspective view illustrating the manner of operating the apparatus of the present invention; 
       FIG. 15  is a diagrammatic side view illustrating the manner of operating the apparatus of the present invention; 
       FIG. 16  is a diagrammatic plan view of a strip-like blade blank; 
       FIG. 17  is a diagrammatic view exemplifying the conventional method of curving a blade blank; 
       FIG. 18  is a diagrammatic view illustrating the conventional roller system of curving a blade blank; and 
       FIG. 19  is a diagrammatic plan view of a curved blade blank available in commerce. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring to  FIGS. 1 and 2 , an apparatus embodying the present invention will be more particularly described by way of example: 
   The apparatus includes a box  2 , a working table  3  thereon, and a pair of pressers  4 ,  5  whose heads project through a slit  21  produced in the top surface of the working table  3 . The pressers  4  and  5  include a body  6  and an arm portion  7 , respectively, each accommodated in the box  2  as shown in  FIG. 2 . The presser  4  has a press face  4   a , and the presser  5  has a press face  5   a  mating with the press face  4   a  when a blade blank is inserted therebetween. 
   The body  6  includes a column portion  9 , and is moved to the left and right in  FIG. 2  by means of handles  14 A and  14 B, thereby adjusting an angle at which the press face  4   a  is faced to the press face  5   a  of the presser  5 . The column portion  9  is provided with known connectors  10  (their details are omitted for simplicity) each having a threaded bore  11 , the connectors  10  being rotative around their axis. 
   Each of the handles  14 A and  14 B has a threaded bar  13 A and  13 B, respectively, engageable with the threads of the bore  11 A and  11 B, the threaded bar  13 A being passed through a side wall  12 A of the box  2 . Likely, the threaded bar  13 B is passed through a side wall  12 B. The threaded bars  13 A and  13 B advance and retreat in accordance with a clockwise or counter-clockwise rotation of the handles  14 A and  14 B, thereby adjusting an angle of decline of the press face  4   a  of the presser  4  against the press face  5   a  of the presser  5 . 
   The arm portion  7  of the presser  5  is rotatively supported by a shaft  15 , and includes an eccentric cam unit  8  that consists of a rotary cam  18  fixed to a rotary shaft  17  of an electric motor  16 . The rotary cam  18  is housed in a hole  19  with a free space. When the rotary cam  18  is driven by the motor  16 , the cam  18  is caused to slide in the arrow direction on and along the periphery of the hole  19 , so that the arm portion  7  is caused to rotate around the shaft  15 . As a result of the rotary movement of the arm portion  7 , the presser  5  is caused to approach and separate from the presser  4 . The motor  16  is operated by a switch  16  ( FIG. 2 ). 
   As shown in  FIG. 3 , a blade blank (pre-processed at this stage)  1  has a rim having an edge  12 , and a flat side having slits  22  at intervals along the rim. Each slit  22  has a bottom  23 , spaced from the edge  12  by H 2 , in contrast to the full width H 1 . The width H 2  is not larger than one half of the width H 1 . 
   As shown in  FIGS. 4A and 4B , the blade blank is inserted between the pressers  4  and  5 ; more exactly, between the two press faces  4   a  and  5   a . An enlarged view is shown in  FIG. 8 .  FIG. 3  indicates the relationship between the press face  4   a  and the blade blank, especially the slit  22 . Each of the press faces  4   a  and  5   a  can have various surfaces, such as flat or convex, depending upon the hardness of the blade blank. As clearly shown in  FIG. 4B , the space between the press faces  4   a  and  5   a  diverge upward, because the space is defined by the slant press faces  4   a  and  5   a . The outside wall  13  of the blade blank is initially straight as shown in chain line  13 , and is scraped under the pressure provided by the press faces  4   a  and  5   a  as shown in solid line  13 . In this way the top end of the blade blank is sharpened as a whole. 
   In the illustrated example the press face  4   a  is inclined at θ 1  in contrast to the straight sidewall of the blade blank, and the press face  5   a  is equally inclined at θ 2 , wherein θ 1  and θ 2  are the same angle but they can be different when desired. 
   Now, the manner of curving a blade blank by the illustrated apparatus: 
   Referring to  FIGS. 2 and 4A , after the pressers  4  and  5  become separated, the blade blank is vertically suspended between the pressers  4  and  5  with its edge  12  downward. At this stage the motor  16  is started. The presser  5  is rotated in the arrow direction F in  FIG. 4 . The strip kept into contact with the press face  4   a  of the presser  4 , so that the blade blank extends in length under the compression. The reduction in thickness under the compression is indicated by (d) in  FIG. 4B . 
   As described above, the press faces  4   a  and  5   a  diverge upward with respect to the outside wall of the blade blank, so that the compressive force focuses upon a point near the edge  12 . As the compression increases, a metal flesh near the edge  12  is elongated longer than a metal flesh portion away from the edge  12 . The diverging of the press faces  4   a  and  5   a  is effective to accomplish the sharp edge  12  because of the focused compressive force to around the edge  12 . 
   Then, the process advances to the step where the edge  12  is curved so as to achieve the curved blade blank as shown in  FIG. 5 . The process is conducted by passing the blade blank consecutively in the direction (a) between the pressers  4  and  5  by N 1 , N 2 , N 3  . . . Nn. The compression is applied to each part N, N 2 , N 3  . . . Nn. In this way the whole length or a predetermined range of the blade blank is curved as a whole. It is not essential to apply the compression continuously to every part N 1 , N 2 , N 3  . . . Nn, but it is possible to provide non-compression zones by placing spaces between adjacent parts. 
     FIG. 9  diagrammatically shows one example of a possible shape of the blade blank, characterized by a valley portion P 1  and hill portions P 2  and P 3  with the valley portion P 1  interposed therebetween. 
     FIGS. 11 to 13  indicate the process of obtaining a special type of blade  1  mounted on a rotary die block  100  illustrated in  FIG. 14 .  FIG. 11  shows a framework-like blade  1  obtained by curving the blade blank. As evident from  FIG. 11 , the edge  12  is placed on the same plane throughout its length. 
     FIG. 12  shows a modified blade in which the blade  1  is partly raised by means of the pressers  4  and  5  in the manner shown in  FIG. 5 . The example of  FIG. 12  has its one side alone raised or curved upward, and the example of  FIG. 13  has its both sides raised. 
   The curving can be started at any point along the blade blank, and continued in any range, at its full length or at a part of it. In this case, the same pair of pressers  4  and  5  having the press faces  4   a  and  5   a  as shown in  FIG. 8  can be employed. 
   Another modification can be also possible by a process shown in  FIG. 6 , where the pressers  4  and  5  have sharpened tops whose ends provide press faces  4   a  and  5   a .  FIG. 7  shows a further modification where the pressers  4  and  5  have flat sides  4   b ,  5   b . The blade blank rests on the flat side  4   b  as shown in  FIG. 7 . Then it is possible to curve by the paired pressers  4  and  5  the blade blank at a position where it has been bent rectangularly. In this case, the pressers  4  and  5  are also carried on the body  6  and arm portion  7  shown in  FIG. 2 . 
   An example shown in  FIG. 10  is unique in having a wavy edge  12 . This modified edge  12  is used as a rotary die blade for perforating a material such as paper and cloth to facilitate separation. 
   In the example shown in  FIG. 2 , the presser  5  is moved in accordance with the rotation of the shaft  15 , and drawn to the other presser  4  or separated therefrom, as the case may be. It is possible to move the presser  5  toward the presser  4  in accordance with the straight movement of the arm  7 . 
   According to the present invention, a straight blade blank can be curved over its full length like an arch or over a predetermined length. When the blade is given a wavy edge as shown in  FIG. 10 , it can be used as a rotary die blade to perforate a work such as paper and a metal sheet. The operation of the apparatus of the present invention can be computerized, thereby allowing an unskilled operator to operate the apparatus.