Abstract:
A staple-former ( 11 ) in a stapler ( 1 ) that uses a driver blade ( 10 ) to drive staples ( 17 ), preferably into a sheaf of paper ( 16 ). The stapler contains a magazine ( 7 ) of staple blanks ( 8 ). A feed device ( 6 ) advances staple blanks onto an integral bending die ( 15 ) for bending into staple shape. Each staple has a first and a second leg ( 18, 19 ) and a crown portion ( 20 ). The staple-former ( 11 ) includes first and second leg-bending parts ( 24, 26 ) and crown-forming part ( 28 ). A staple forms when a drive device ( 12, 13, 14 ), moves the leg-bending parts ( 24, 26 ) and the crown-forming part over the bending die ( 15 ) causing a staple blank ( 8 ) to assume a staple shape. The staple-former then reciprocates to its starting positions, the staple advances to the driver blade ( 10 ), and a biasing element ( 32 ) urges the crown-forming part ( 28 ) away from the staple-former ( 11 ).

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
   The present application claims priority to Swedish Patent Application No. 0103048-5 filed 14 Sep. 2001. Said application is expressly incorporated herein by reference in its entirety. 
   BACKGROUND OF INVENTION 
   1. Technical Field 
   The present invention relates to a staple-former in a stapler in which staples are driven by a driver blade into a workpiece, preferably a sheaf of paper. The stapler contains a staple magazine in which longitudinally extended staple blanks are stored. The staple blanks are advanced onto an integral bending die by a feed device contained in the stapler. The bending die has an upper support surface over which the staple blanks are bent by a staple-former into staple shape. This staple shape includes a first and a second leg with an intermediate crown portion. The staple-former has a first leg-bending part and a second leg-bending part with an intermediate crown-forming part that exhibits a stamping surface. The formation of a staple is accomplished by the staple-former being driven by a drive device that is integrated into the stapler from an starting position in a staple-forming motion in a direction that is transverse to the direction of extent of the support surface. During this motion, the staple-former is brought against the bending die, whereupon the leg-bending parts over the bending die bend the staple blank into a staple shape. In a continuation of this motion, the staple-former is advanced a distance such that the stamping surface of the crown-forming part presses the crown portion of the staple blank against the support surface. After this, the staple-former is reciprocated by the drive device back the starting position and the bent staple that has been formed is fed forward to the driver blade. 
   2. Background of the Invention 
   Staple-formers of the type described above are generally known. Such a staple-former is exemplarily described in the Swedish patent application SE 9201230-1. A disadvantage of earlier staple-formers is that they require extremely precise regulation of the staple-forming motion, since it is very important that the staple-former undergo reciprocation within an extremely narrow tolerance range. If reciprocation occurs too early, the crown-forming part will not press the staple crown against the bending die, and the staple blank will not be bent sufficiently and this often causes the stapler to jam. If reciprocation occurs too late, the crown-forming part will strike the bending die with great force, which damages the staple while at the same time causing the staple-former and drive device to wear much more rapidly. To counteract the aforesaid disadvantages, solutions have previously been proposed in which the stapler is equipped with damping devices that damp the staple-forming motion before reciprocation occurs. These devices are often complicated and expensive to fabricate, and they fail to solve the problems that arise when reciprocation occurs too early. 
   Another disadvantage of existing staple-formers is that, since they are usually driven by the same drive device that drives the driver blade, the staple-former must be adjusted precisely in relation to the driver blade, which can often be an extremely difficult task to perform. 
   The present invention overcomes these disadvantages by means of a staple-former of a type in which the crown-forming part is displaceably connected to the staple-former by means of an intermediate biasing means, also referred to as an elastic element and/or a take-up device or means. In a preferred embodiment, the elastic element takes the form of a leaf spring bent into a hairpin shape. Further in this preferred embodiment, the crown-forming part is displaceably connected to the staple-former by means of a guide arrangement. Still further, the staple-former exhibits an integrated driver blade. The biasing means or elastic element is configured or selected so that the biasing force exerted thereby is sufficiently high to maintain the crown-forming part in an extended position through out the bending of a staple blank over the bending die, but also sufficiently weak to permit the crown-forming part to retract into the body of the staple-former when the staple bending process has been completed, but the staple-former continues to be driven toward the bending die. 

   
     BRIEF DESCRIPTION OF DRAWINGS 
     The invention will be described below with reference to the accompanying figures, in which: 
       FIG. 1  is a schematic view, shown in partial cut-away, of a stapler according to the present invention; 
       FIG. 2  is an elevational view of a staple blank bent into staple shape; 
       FIG. 3  is a perspective view showing the staple-former and bending die of the invention, and on which an unbent staple blank is placed; 
       FIG. 4  is a side elevational view corresponding to  FIG. 3 ; 
       FIG. 5  is a cross-section view taken along the line A—A shown in  FIG. 3 ; 
       FIG. 6  is a perspective view corresponding to  FIG. 3 , in which bending of the staple blank has begun; 
       FIG. 7  is a perspective view corresponding to  FIG. 3 , but in which the staple-former has been moved an additional distance relative to  FIG. 6 ; 
       FIG. 8  is a perspective view showing s the staple-former in the position in which the staple blank has been fully bent; and 
       FIG. 9  is a side elevational view of the arrangement shown in  FIG. 8 . 
   

   DETAILED DESCRIPTION 
   A preferred embodiment of the invention will hereinafter be described with reference to the accompanying drawings. In that regard,  FIG. 1  shows a stapler arrangement  1  that includes a base part  2  to which a stapler head  3  is pivotably connected by means of a pivot shaft  4 . The base part  2  is equipped with a staple anvil  5  and a feed device  6 . A staple magazine  7  is arranged in the stapler head  3  and contains longitudinally extended staple blanks  8  whose long sides are joined to one another to form an extended band that is arranged into a roll shape  9  in the illustrated embodiment. In the stapler head there is arranged a driver blade  10 , which is integrated with a staple-former  11 , also referred to as a staple forming arrangement  11 . 
   The staple-former  11  is interconnected with drive arms  12 , but only one of which is shown in  FIG. 1 . With regard to the descriptions contained herein, the terminology interconnected should be taken to indicate that a connection exists between the so-described elements, but that connection may be direct or indirect; that is, there may be other components or elements interstitially positioned along the connection that is so described. The drive arms  12  are pivotably mounted in bearings on the pivot shaft  4 . A drive motor  13  is arranged on the base part  2  that is connected to the drive arms  12  by means of a transmission device  14 . In the stapler head  3 , a bending die  15  is arranged over which the staple blanks  8  are bent by the staple-former  11  into staple shape in a manner that will be clarified in the description below.  FIG. 1  also shows a workpiece  16  that is to be stapled, and which preferably consists of a sheaf of papers. The drive arms  12 , drive motor  13  and transmission device  14  form a drive element which, in a manner that is known, drives the stapler head  3 , the driver blade  10  and the staple-former  11  in an up-and-down stapling motion that is identified by the double headed arrow A. 
     FIG. 2  shows a staple blank  8  that is bent into staple shape  17 , which shape exhibits a first leg  18  and a second leg  19  which are substantially parallel, and has an intermediate crown portion  20 . 
     FIGS. 3 and 4  depict in detail the staple-former  11 , the bending die  15  with a staple blank  8  placed thereon, and the driver blade  10 . The bending die  15  exhibits an upper support surface  21 , whose direction of extension is indicated by the arrows B and C. The direction of motion of the staple-former is also indicated in this figure by a double arrow A and, as can be seen, this direction of motion is transverse to the direction of extension of the support surface B, C. The staple-former  11  comprises a plate-shaped base part  22  that has recesses  23  for the drive arms  12 , but which are not shown in this Figure. The staple-former  11  further exhibits a first leg-bending pan  24 , which is integrated with the base part  22  and exhibits a bending surface  25 , and a second leg-bending part  26 , which is also integrated with the base part  22  and exhibits a bending surface  27 . The base part  22 , also referred to as a main body portion  22  of the staple forming device  11 , exhibits a driver blade  10  which, as is mostly clearly seen in  FIG. 4 , constitutes an integral part of the base part  22  of the staple-former  11 . Between the leg-bending parts or portions  24  and  26  there is arranged a crown-forming part or portion  28  that exhibits a stamping surface  29  facing the bending die. The crown-forming part  28  is displaceably connected with the staple-former  11  via a first guide arrangement  30  and a second guide arrangement  31 , whose directions are indicated by the double arrow D, whose direction is in agreement with the direction of the double arrow A, so that the crown-forming part can thus move in the direction indicated by the double arrow A. 
   On its side facing the stamping surface  29 , the crown-forming part is connected with an elastic element  32 , also referred to as a take-up means or device, and which is exemplarily depicted in the Figures as a leaf spring  33  bent into a hairpin shape. The leaf spring  33  is, at its opposite end  34  from the crown-forming part, fixedly connected to the base part  22 . This fixed connection can be realized by welding, soldering, riveting or in any other way known to one skilled in the art that offers the necessary strength. The leaf spring  33  is inserted in a gap or hole  35  realized in the base part  22 , but it will be apparent to one skilled in the art that the leaf spring can be arranged so that it extends to the left in  FIG. 4  rather than to the right, as is now shown, meaning that the base part need not be provided with the hole  35 . 
     FIG. 5  shows the connection of the crown-forming part  28  with the staple-former  11 . As is shown, the crown-forming part  28  is in abutment with the driver blade  10 . The figure further shows that the guide arrangement  30  exhibits a first sliding surface  36  arranged on the first leg-bending part  24 . A second sliding surface  37  is arranged on the crown-forming part  28  and the sliding surfaces are in sliding contact with one another. The guide arrangement  31  exhibits a third sliding surface  38  on the second leg-bending part  26  and a fourth sliding surface  39  arranged on the crown-forming part  28 ; these sliding surfaces are also in sliding contact with one another. Because the surfaces  36  and  38  are inclined toward one another in the manner shown in  FIG. 5 , while the surfaces  37  and  39  are similarly inclined toward one another, it is ensured that the crown-forming part  28  cannot be separated from the driver blade  10  in the direction indicated by the arrow F, thus guarantying that the crown-forming part will be ensured a specified path of motion between the guide arrangements  30  and  31 , in abutment with the driver blade  10 . 
   The invention will now be described with reference to  FIGS. 1–9  by describing a stapling cycle. When a workpiece  16  is to be stapled, it is placed on the staple anvil  5 , at which point the stapler  1  is in its starting position, which is shown in  FIG. 1 . The positions of the staple-former  11  and the driver blade  10  are shown in  FIG. 3 . In this position the feed device  6  has advanced the staple band  9  onto the bending die to a position such that a staple blank  8  is situated beneath the staple-former at the same time as a blank that has been formed into staple shape  17  has been advanced to a position in front of the bending die  15 , as is most clearly shown in  FIGS. 3 and 4 . 
   The drive device  12 ,  13 ,  14  provides an exemplary embodiment of what is referred to herein as a drive means, an arrangement which drives the stapler head  3  downward in the direction indicated by the double arrow A and into abutment with the workpiece  16 , whereupon the stapler head comes into contact with the feed device  6 . The staple-former  11  and the driver blade  10  remain in the positions shown in  FIG. 3  during this time. The drive device  12 ,  13 ,  14  thereafter continues driving the staple-former  11  downward in the direction of the double arrow A. In the course of this downward motion, the bending surfaces  24  and  26  strike the staple blank, which is bent over the bending die  15  and as is depicted in  FIG. 6 . The driver blade simultaneously drives the staple  17  downward into the workpiece  16 ; but this is not shown in  FIG. 6 . The downward motion continues thereafter through the position shown in  FIG. 7  and, in this position, the staple blank  8  has been bent further and the stamping surface  29  has come into contact with the crown portion  20  of the staple blank  8 . The downward motion is completed once the staple-former reaches the position shown in  FIG. 8  and, in this position, the staple-former has been driven far enough downward that the stamping surface  29  presses the crown portion  20  of the staple blank against the support surface  21  of the bending die, whereupon the staple blank is formed into staple shape. 
   In this position, the crown-forming part  28  has moved in opposition to the force from the elastic element  32  and upwards relative to the base part  21  in the direction of the double arrow D, thus placing the elastic element  32  under tension as shown in  FIG. 9 . In this position the driver blade  10  has driven the staple  17  completely into the work piece  16 . The drive device  11 ,  12 ,  13  is thereafter reversed in a manner known to one skilled in the art, and the staple-former and stapler head resume their positions as shown in  FIG. 3  and  FIG. 1 , respectively, and the tensioned elastic element returns the crown-forming part  28  to the position shown in  FIG. 3 . During this return motion, the feed device  6  advances the staple band one step forward, whereupon a new stapling sequence can be carried out. The elastic element is designed so as to ensure that the stamping surface  29  presses the staple crown  20  against the support surface  21  with sufficient force, and that this force must be varied depending on the properties of the staple material. 
   In the foregoing description, the staple shape has been presented as a staple with two substantially parallel legs and an intermediate straight crown portion. It will be obvious to one skilled in the art that the straight crown portion can consist of an arched portion and that, in such a case, the bending die and stamping surface will be realized in arched form. Furthermore, the elastic element has been presented as a hairpin-shaped leaf spring, but it will also be obvious to one skilled in the art that the elastic element may consist of a helical spring whose two ends are secured to the staple-former and the crown-forming part, respectively.