Patent Publication Number: US-6981667-B2

Title: Elliptical acetabuliform blade for shredder

Description:
FIELD OF THE INVENTION 
   The present invention relates to an improved cutting blade for a shredder, especially to an elliptical acetabuliform blade that is integrally formed by punching a sheet metal in a mold machine. 
   BACKGROUND OF THE INVENTION 
   The conventional shredders for cutting paper use a plurality of cutting blades and spacers engaging over a rotary cutter shaft, and the shearing force that two parallel and opposite rotary cutter shafts produce for transferring and cutting the paper-to-be-cut along a longitudinal direction into strips. Shredders can be classed into two types, the stripe-cut shredders and crosscut shredders, according to the machine cutting style. The former shredders arrange cutting blades to the rotating cutter shafts in a manner to cutting the paper in a longitudinal direction to form strips. The later shredders include blades that include more than one cutting edge, and each cutter is disposed helically along the rotary cutter shaft for first cutting paper along a longitudinal direction into strips and then cutting paper along a horizontal direction into approximate 4 mm×40 mm paper chips. 
   By referring to the assembled perspective view of a conventional blade illustrated in  FIG. 1  and a planar view showing the operation of the conventional blade in  FIG. 2 , the conventional blade is made by punching a sheet metal having a thickness of approximately 2 mm into a circular blade by a mold. The blade includes a polygonal central hole A 1  through which a rotary shaft may pass. The blade also includes cutting edges A 2  that are spaced in 120 degrees apart around the periphery. As shown, when two blades are arranged on the rotary shafts B in a back-to-back manner to combine into a set of blades A, the cutting edges of the two blades assume a V-like edge A 3 . The opposite rotary shafts B′ space the two blades apart by spacer (not shown) in a face-to-face manner to form a set of blade A′. When the paper-to-be-cut passes through the two reverse rotary shafts B, B′, the opposing rotation of the periphery of the blades, that is, flanks A 4  and flanks A 4 , will cut the paper like scissors. The opposing rotation of cutting edges A 2  and the opposite flanks A 4  will then cut the paper along a horizontal direction into 4 mm×40 mm paper chips. 
   During operating of the conventional blades, to ensure smooth cutting of the paper along the horizontal direction, sharp blades with proper orientations are needed. However, because the blades are formed by a punch molding, the mold wear that increases with the time will reduce sharpness of the blade edges, which does not improve until replacing the mold, to result in inconsistent quality. To ensure quality of the blades, it is necessary to shorten the service term of the mold, which results in increment of the cost. In addition, in the conventional blades, the thickness of the blade is the same as the width of the paper-to-be-cut. To ensure the strength of blades while cutting along the horizontal direction, the blades cannot be too thin, or else the blades tend to deform or fracture. Such a limitation attributes to the high material cost, which is less competitive as compared to the current market price. In addition, because the thickness of the conventional blades is same as the width of the paper-to-be-cut, and because the location of the width define the horizontal cutting points, the narrower width of cross-section is, the smaller output power is needed to cut along the horizontal direction. In other words, the motor can supply a minimum power for cutting along the horizontal direction, that is, to reduce the power consumed by the motor. But because of the width of the paper-to-be-cut by the conventional blades is 4 mm, the motor needs to output higher power to drive the blades and flanks moving in opposing directions to cut the paper along the horizontal direction smoothly. 
   SUMMARY OF THE INVENTION 
   In view of the above, this invention overcomes the shortcoming of the conventional blades. 
   The main objective of the present invention is to provide an elliptical acetebuliform blade for shredders, that is integrally punched from a sheet metal in a mold into an elliptical acetabuliform blade to effectively reduce the material cost and the weigh of the blade to thereby reduce the motor loading and power consumption. 
   Another objective of the present invention is to provide an elliptical acetabuliform blade for shredders, that uses the change in the curvature of the elliptical acetabuliform blade to cut paper into paper chips each having a wider center and tapering towards the ends, so as to reduce the power that that motor needs to output for cutting the two ends to thereby reduce the motor loading and the power consumption. 
   To realize the above objectives, in the present invention, a sheet metal is punched by a mold to integrally form an elliptical acetabuliform blade, where the periphery of elliptical blade is integrally formed into serration. The serrated periphery extending horizontally inwards to integrally form a planar disk for cutting paper along a longitudinal direction serves as a flank. The two ends along the major axis of the elliptical of the flank are integrally formed into a hooked edge for cutting the paper along a longitudinal direction to form paper chips having double-tapering ends. An inner edge of the flank then integrally extends inwards and downwards to form an arc base and then a circular base. A polygonal hole is formed in a center of the circular base, through which a rotary shaft may pass. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is an assembled perspective of a conventional shredder; 
       FIG. 2  is a planar view of a conventional shredder in operation; 
       FIG. 3  is the a planar view of the elliptical acetabuliform blade of the present invention; 
       FIG. 4  is a cross-sectional view taken along lines  4 — 4  in  FIG. 3 ; 
       FIG. 5  is a cross-sectional view taken along lines  5 — 5  in  FIG. 3 ; 
       FIG. 6  is a perspective view of the elliptical acetabuliform blade assembled to the rotary shafts; 
       FIG. 7  is an operating view of the elliptical acetabuliform blade of the present invention in cutting paper; 
       FIG. 8  is an operating view of the elliptical acetabuliform blade of the present invention in cutting off paper; 
       FIG. 9  is a schematic view of the elliptical acetabuliform blade of the present invention fragmenting paper after cutting; and 
       FIG. 10  is a schematic view showing the paper after being cut by the elliptical acetabuliform blade of the present invention. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   The present invention will be described in further detail hereinafter, with reference to accompanying drawings. 
   Please refer to  FIGS. 3 to 5 , where  FIG. 3  illustrates the planar view of the present invention, and  FIGS. 4 and 5  are cross-sectional views taken from lines  4 — 4  and line  5 — 5  in  FIG. 3 , respectively. The above-mentioned views disclose a revolutionized cutting blade  1  for a shredder, which blade is able to provide an optimum sheet capacity based on the various types of shredders. The present invention selects a sheet metal having a thickness of 0.2 mm as a raw material, the selected sheet metal is punched into an elliptical acetabuliform blade by a mold. The periphery  11  (shown in the enlarged view of  FIG. 3 ) of the elliptical blade is integrally formed into serration  110 . The periphery  11  of serration serves to pull the paper-to-be-cut downwards. The acetabuliform periphery  11  extending horizontally inwards to integrally form a planar disk for cutting paper along a longitudinal direction serves as a flank  12 . The two ends along the major axis of the elliptical flank  12  are each integrally formed into a hooked edge  13  for cutting the paper along a longitudinal direction to form paper chips having double-tapering ends. An inner edge  120  of the flank  12  integrally extends inwards and downwards to form an arc base  14  and then a circular base  15 . A polygonal hole  16  is formed in a center of the circular base  15 , through which a rotary shaft may pass. 
   As shown in the assembled perspective view of the present invention in  FIG. 6 , the standardized elliptical acetabuliform blades punched from a sheet metal by a mold are arranged sequentially on two rotary shafts to be assembled into the rotary cutting tool that is most important for a shredder. During assembly, the elliptical acetabuliform blades on one of the rotary shafts are arranged by alternating in forward and reversed orientations. The elliptical acetabuliform blades on the other rotary shaft are then arranged by alternating in reversed and forwards orientations. 
   As exemplified in  FIG. 6 , the first blade  21  and the second blade  22  on a lower first rotary shaft  2  are arranged by alternating in the forward and reversed orientations. Because the blades extend from an inner periphery of flank inwards and downwards to form an arc base and then a circular base, the circular base of the first blade  21  and second blade  22  join to contact each other while the hooked edges of the first blade  21  and the second blade  22  are separated from each other to assume an open space  23 . On the other hand, the first blade  31  and second blade  32  on an upper second rotary shaft  3  are arranged by alternating in the forward and inversed orientations. Similarly, because the blades extend from the inner periphery of the flanks inwards and downwards to form an arc base and then a circular base, the circular base of the first blade  31  and second blade  32  are separated from each other, while the hooked edges of the first blade  31  and the second blade  322  are joined to contact each other. By adopting such arrangement, when the two rotary shafts rotate in opposing directions, the hooked edges  33  of the first blade  31  and the second blade  32  on the upper second rotary shaft  3  after contacting each other adapt to insert into the open space  23  of the first blade  21  and second blade  22  on the lower first rotary shaft  2 . 
   As shown in the operating views in  FIGS. 7 and 8 , the standardized elliptical acetabuliform blades enable the flanks of the corresponding blade set to maintain a certain contact gap at all time by means of the changes between the major axis and minor axis of the elliptical blades and the curvatures of the blades. In other words, while viewing from the rear projection, the superposition of the blades arranged on different rotary shafts are constant. Such a constant superposition can ensure scissors like cutting effects between the flanks  12  when the two rotary shafts rotate in opposing directions (shown in  FIG. 7 ). When the cutting edges  13  of the corresponding opposite blades on the two ends of elliptical major axis rotate to the elliptical major axis, the hooked edges  13  on the major axis of the elliptical blades will cooperate with the flanks  12  on the minor axis of the mating elliptical blades to cut off the paper strips (as shown in  FIG. 8 ). 
     FIGS. 9 and 10  illustrate the schematic views of the elliptical acetabuliform blade of the present invention fragmenting paper after cutting, and the paper after being cut by the elliptical acetabuliform blade of the present invention. Along with the changing of the curvatures of the elliptical acetabuliform blades, the paper is fragmented into paper chips  4  each having a wider center  42  and tapering towards the ends  41 . Because of the two ends  41  of the paper chip  4  are the horizontal cutting positions, the narrower width of cross-section is, the smaller output power is needed to cut along the horizontal direction. In other words, the motor can supply a minimum power for cutting along the horizontal direction under a minimum load. The reduction in the motor load also reduces the power consumption and increases service-life of the motor. 
   In addition, the conventional blade is punched from a sheet metal having thickness of about 2 mm, while the elliptical acetabuliform blade of the present invention may be punched from a sheet metal having a minimum thickness of 0.2 mm, where the costs of the two materials are significantly different, and the reduced weight also helps to further reduce the power that the motor needs to supply to thereby increase the service-life of the motor and reduce the power consumption. These characteristics help to reduce the manufacturing cost and enhance the market competitiveness. 
   In summary, according to the present invention, a sheet metal may be punched into elliptical acetabuliform blades, where the periphery of each elliptical blade is integrally made into serration. The serrated periphery extending horizontally inwards to integrally form a planar disk for cutting paper along a longitudinal direction serves as a flank. The two ends along the major axis of the elliptical flank are each integrally formed into a hooked edge for cutting the paper along a longitudinal direction to form paper chips having double-tapering ends. The revolutionized construction of the present invention reduces power consumption, material cost, and lessens motor load, so as to enhance the market competitiveness of the shredder. 
   In the present specification “comprises means “includes or consists of” and “comprising” means “including or consisting of”. 
   The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, as appropriate, may, separately, or in any combination of such features, be utilized for realizing the invention in diverse forms thereof. 
   
     
       
         
             
           
             
                 
             
             
               LISTING OF NOMENCLATURES 
             
             
                 
             
           
          
             
                 
             
          
         
         
             
             
             
          
             
                 
                1 cutting blade 
               11 periphery 
             
             
                 
               110 serration 
               12 flank 
             
             
                 
                13 cutting edge 
               14 base 
             
             
                 
                15 base 
               16 polygonal hole 
             
             
                 
                2 first rotary shaft 
               21 first blade 
             
             
                 
                22 second blade 
               23 open space 
             
             
                 
                3 second rotary shaft 
               31 first blade 
             
             
                 
                32 second blade 
               33 hooked edges 
             
             
                 
                4 paper chips