Abstract:
A sheet cutting device, including a cutter blade to cut a bundle of sheets by moving at a slant whose component is a compound of moving perpendicular to the surface of the bundle of sheets and simultaneously parallel to the surface of the bundle of sheets, a supporting member to support the bundle of sheets for cutting, wherein the supporting member includes a supporting surface to support the bundle of sheets and an edge section perpendicular to the supporting surface; and a pressing member to press the bundle of sheets on the supporting member, wherein the cutter blade moves along the edge section and protrudes beyond the supporting surface so that the cutter blade cuts through the whole bundle of sheets, and wherein the clearance between the edge section and the cutter blade is 0.0 to 0.5 mm.

Description:
[0000]     This application is based on Japanese Patent Application No. 2004-306485 filed on Oct. 21, 2004 in Japanese Patent Office, the entire content of which is hereby incorporated by reference.  
       BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates to a sheet cutting device which cuts a plurality of sheets, and in particular, to a sheet cutting device which can be installed in an image forming system, such as a copy machine, a printer, a facsimile, and a compounded apparatus which includes more than two functions of the above functions.  
         [0002]     As the sheet post-processing device which is installed in a system of the image forming apparatus, apparatuses have been developed which produce booklets via bundling a plurality of sheets. In most of the sheet post-processing devices, the bundles of sheets are folded at their central sections, then bound at the central sections, after which, facing sections to the bound sections, that is, the edges opposite the bound edges are cut by the sheet cutting device, resulting in a uniformly edged booklet.  
         [0003]     Since the sheet cutting device to be installed in the sheet post-processing device is structured as part of the image forming apparatus installed in copy centers or offices, it must be small-sized, as well as working with low power consumption, and further, it is necessary that the function to produce uniformly edged booklets is always maintained. If the cut edges are uneven, or uncut portions remain, the booklet cannot be opened smoothly, which is of course a major problem.  
         [0004]     On the other hand, a sheet cutting apparatus used in the production process of a great number of the same booklets, such as printed matter, is a large-scale operation and driven by great electric power, accordingly, such sheet cutting apparatus need only be good enough to exhibit high cutting performance. However, concerning the sheet cutting device used as a part of the image forming apparatus, the essential condition is that the device is operable with small electric power, and is small in overall size. Therefore, design in ingenuity is necessary to perform functions beyond the large-scale sheet cutting apparatus. 
        Japanese Unexamined Patent Publication No. 2003-136471 (hereinafter referred to as the Patent Document 1) discloses a sheet cutting device wherein the sheets are trimmed by a cutter which is pressed against the sheet surface at a slant, as the sheet cutting device which can be used in a business machine.        
 
         [0006]     In the sheet cutting device described in Patent the Document 1, in order to cut the sheets, the cutter is pressed at a slant onto the sheets placed on a cutting table. In this cutting method, the component of force is parallel to the surfaces of the sheets, therefore, the sheets are liable to be more misaligned during the cutting process.  
         [0007]     In order to cut the bundle of sheets in such a manner that the edges of the bundle of sheets are flat, the above-described misalignment parallel to the surface of the sheets must be prevented. In the case of the Patent Document 1, the above-described misalignment is often generated because of the slanted movement of the cutter. For this purpose, the bundle of sheets are pressed by a force of about 1 ton. However, when the bundle of sheets are cut, while being pressed by such great force, the pressure mark due to the pressure deformation is generated on the edges of the sheets, which is a drawback.  
         [0008]     The generation of the pressure mark will now be explained referring to  FIG. 1 .  
         [0009]     After bundles of sheets SS are sandwiched between supporting plate ST and pressure member PM, bundle of sheets SS is pressed by force F of pressing member PM. Since pressing force F is about 1 ton, the sheets are bent at boundary section SC which is between edge section SA being a tear-off section and also a non-forced section and pressed section SB (See  FIG. 1 ).  
         [0010]     The sheets are cut away at edge section SA from boundary section SC. After the cutting procedure, when edge section SA being a trimmed section is long, pressure marks are generated near the cut edges of bundle of sheets SS, which are due to bending of boundary section SC. Therefore, the edges of bundle of sheets SS are misaligned, which decrease the appearance of the bundle.  
       SUMMARY  
       [0011]     There thus exists a need to overcome the above problem.  
         [0012]     The present invention provides,  
         [0013]     a sheet cutting device, including:  
         [0014]     a cutter blade to cut a bundle of sheets by moving at a slant whose component is a compound of moving perpendicular to the surface of the bundle of sheets and simultaneously parallel to the surface of the bundle of sheets,  
         [0015]     a supporting member to support the bundle of sheets for cutting, wherein the supporting member includes a supporting surface to support the bundle of sheets and an edge section perpendicular to the supporting surface; and  
         [0016]     a pressing member to press the bundle of sheets on the supporting member,  
         [0017]     wherein the cutter blade moves along the edge section and protrudes beyond the supporting surface so that the cutter blade cuts through the whole bundle of sheets, and  
         [0018]     wherein the clearance between the edge section and the cutter blade is 0.0 to 0.5 mm. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]      FIG. 1  is a drawing to illustrate generation of the pressure marks.  
         [0020]      FIG. 2  shows the structure of the sheet cutting device relating to the embodiment of the present invention.  
         [0021]      FIG. 3  is a cross sectional view of the cutting section.  
         [0022]      FIG. 4  is an enlarged cross sectional view of the cutting section.  
         [0023]      FIG. 5  is an enlarged cross sectional view of a cutter unit supporting section. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0024]     The embodiments of the present invention will now be described below referring to the drawings, however, the present invention is not limited to the described embodiments.  
         [0025]      FIG. 2  is a front view of the sheet cutting device, while  FIG. 3  is a cross sectional view of the cutting section.  
         [0026]     On the upper section of sheet cutting device  100 , shaft  108  supported by frame  100 A of sheet cutting section  100  is mounted (see  FIG. 2 ). Male screws  108 A and  108 B, which rotate in opposite direction, are mounted on shaft  108 , and further male feed screw  108 A is engaged within female screw unit  106 , while male screw  108 B is engaged within female screw unit  107 .  
         [0027]     Vertically movable pressing member  101  and female screw units  106  and  107  are connected by connecting arms  104  and  105 . That is, the upper end of connecting arm  104  is supported by female screw unit  106 , while the lower end of connecting arm  104  is supported by the left end of pressing member  101 . Further, the upper end of connecting arm  105  is supported by female screw unit  107 , and the lower end of connecting arm  105  is supported by the right end of pressing member  101 . Since shaft  108  is engaged with motor M 2  via gear G 1 , when motor M 2  rotates, female units  106  and  107  move in opposite directions. And thereby, connecting arms  104  and  105  change their slopes, and pressing member  101  is driven vertically, remaining parallel to the axis of shaft  108 .  
         [0028]     As described above, motor M 2 , female screw units  106  and  107 , and connecting arms  104  and  105  structure a pressing member driving mechanism which drives pressing member  101  vertically.  
         [0029]     Pressing member  101  includes cutter receiving member  101 A, and bundled sheets SS are gripped and secured between cutter receiving member  101 A and supporting plate  102 . Since pressing member  101  is driven by a driving mechanism including male screws  108 A and  108 B under a greatly reduced gear ratio, pressing member  101  presses bundled sheets SS under high pressure, being about 1 ton.  
         [0030]     Rollers  115  and  116  are fixed on cutter unit  103  whose top edge is the blade, and guided by guide members  117  and  118 , both of which are slanted to the right. Guide members  117  and  118  are firmly fixed to frame  100 A.  
         [0031]     Cutter driving member  125  is driven in the horizontal direction via male screws  126  and  127 . Male screws  126  and  127  are driven by motor M 3  via gears G 2 -G 5 . Further, vertical slot  125 A is formed on cutter driving member  125 , and engages two pins  119  which are fixed on end  103 A of cutter unit  103 .  
         [0032]     The driving mechanism of cutter unit  103  is composed of motor M 3 , gears G 2 -G 5 , male screws  126  and  127 , and cutter driving member  125 , whereby cutter unit  103  is driven in the horizontal direction. Cutter unit  103  is raised and lowered by guide members  117  and  118  at an angle in arrowed direction J  
         [0033]     Next, the operation of cutting device  100  will be explained.  
         [0034]     In standby status, pressing member  101  is at its upper limit, being the home position.  
         [0035]     When bundled sheets SS are introduced into cutting device  100 , motor M 2  is activated so that female screw units  106  and  107  move, and thereby, pressing member  101  is lowered. Under the condition that receiving member  101 A presses bundled sheets SS, pressing member  101  stops lowering.  
         [0036]     When the plurality of stacked bundled sheets SS are trimmed, in order to prevent generation of their misalignment due to horizontal force, pressing member  101  evenly presses the whole surface of bundled sheets SS with great force so that they are not misaligned by the horizontal force generated by cutter unit  103 .  
         [0037]     When bundled sheets SS have been completely pressed, motor M 3  is activated which moves cutter unit  103  toward the upper left, shown by arrow J. By this movement of cutter unit  103 , cutter unit  103  goes up from the initial position as shown in  FIG. 3 , and cutter blade  103 B is projected from top surface  102 B of supporting plate  102  to trim bundled sheets SS. Since the cutting action of cutter blade  103 B (see  FIG. 3 ) is performed via sliding of cutter blade  103 B, the cutting action can be performed with a relatively small driving force. In addition, even when a large number of the sheets are cut, the driving force does not change, though the stroke length of the cutter does change.  
         [0038]     After all of the stacked bundles are cut, the cutting edge of cutter blade  103 B comes into contact with cutter receiving member  101 A, whereby, the resistance against the driving force of cutter unit  103  increases. The controller detects the increased current loaded in motor M 2 , caused due to the resistance. That is, it detects the increase of motor driving current, and deactivates driving motor M 2 . The total bundles included in bundled sheets SS are cut in this manner.  
         [0039]     After the edges of the sheets are cut, motor M 1  is reactivated, and rotated in the opposite direction of the above procedure, to retract pressing member  101 . Further, motor M 2  is activated to lower cutter unit  103  to the predetermined position in the lower right of  FIG. 2 , and cutter unit  103  finally stops at the lower limit position, being the home position.  
         [0040]     Supporting plate  102 , which supports bundled sheets SS at the cutting position, is formed of resins, such as polypropylene and polyoxymethylene, and fixed into frame  100 A with plural screws  102 A, at several points in the longitudinal direction (perpendicular to the printed surface of  FIG. 3 ) into supporting plate  102 . The position of supporting plate  102  is secured by block  1021  from the sheet conveyance direction. Block  1021  is fixed with screw  1021 A on frame  100 A. Supporting plate  102  includes top surface  102 B to support bundled sheets SS, and edge  102 C generally perpendicular to top surface  102 B and facing cutter blade  103 B (see  FIG. 4 ), and the position of edge  102 C is precisely secured by block  1021 .  
         [0041]     Numeral  1022 , being an entrance guide for bundled sheets SS, is formed of an elastic film, such as polyethylene terephthalate, and is adhered onto slope section  100 B formed on frame  100 A.  
         [0042]     Cutter blade  103 B is fixed onto cutter holder  103 C by screws  103 D. Just like supporting plate  102 , cutter blade  103 B is secured by plural screws  103 D, at several points in the longitudinal direction (perpendicular to the printed surface of  FIG. 3 ) of cutter blade  103 B. Cutter unit  103 , composed of cutter blade  103 B and cutter holder  103 C, moves upward as shown by arrow K to cut bundled sheets SS.  
         [0043]     Bundled sheets SS are pressed onto supporting plate  102  by pressing member  101 .  
         [0044]      FIG. 3  shows the condition of cutter blade  103 B being at the initial position. Cutter blade  103 B goes up from the position of  FIG. 3 , and protrudes beyond top surface  102 B so that all bundled sheets SS are assuredly cut.  
         [0045]     In addition, as shown in  FIG. 5  (which is an enlarged cross sectional view of circle W in  FIG. 3 ), film sheets  103 E, formed of high-pressure polyethylene film, are sandwiched between cutter holder  103 C and frame  100 A, and thereby, cutter unit  103  moves smoothly in the vertical direction.  
         [0046]      FIG. 4  is an enlarged cross sectional view of the cutting section. Clearance D between cutter blade  103 B and edge  102 C of supporting plate  102  is set less than 0.5 mm. By setting clearance D to be less than 0.5 mm, it is possible to prevent generation of pressure marks on the edges of bundled sheets SS which have been cut, which will now be explained further referring to  FIG. 1 .  
         [0047]     By setting clearance D to be less than 0.5 mm, it is possible to cut bundled sheets SS at the position just on boundary section SC or at the position shown by dotted line L which is almost adjacent to boundary section SC. Consequently, pressure marks due to deformation of the sheet surface caused by the high pressure cannot be generated on the edges of bundled sheets SS, which have been cut.  
         [0048]     AS described above, in order to totally prevent generation of pressure marks on the edge of bundled sheets SS which have been cut, it is preferable that cutter blade  103 B is directly brought into contact with edge  102 C of supporting plate  102 , that is, cutter blade  103 B is raised while clearance D is zero, and cutter blade  103 B is driven to cut bundled sheets SS. Further, it is preferable that right angle  102 D, formed by top surface  102 B and edge  102 C, is not rounded, but sharp edged. Even when right angle  102 D is round shaped, the curvature radius must be to be less than 0.5 mm, by which the generation of the pressure marks is exactly prevented.  
         [0049]     According to the present invention, bundled from dozens of sheets to multiple-thousand sheets which have the high grade edge can be formed. And the generation of the pressure marks which is easy to generate in the vicinity of the cutting position is exactly prevented.