Sheet punching device and image forming apparatus having the same

Abstract

A sheet punching device that cuts holes in a sheet while punches are entering die holes, in which a plurality of punch trains along each of which a plurality of punches are aligned on a rotating shaft in parallel with the rotating shaft are disposed in the rotation direction of the rotating shaft, and the die holes are disposed in correspondence with the punches of the punch trains.

1 - 12 . (canceled)  
   
   
       13 . A sheet punching device, which allows punches to enter die holes to cut holes in sheets conveyed at a predetermined sheet conveying interval, said sheet punching device comprising: 
 a plurality of punch trains, each of which includes a plurality of said punches axially aligned on a rotating shaft and projecting in a radial direction of said shaft,    wherein said plurality of punch trains are disposed with a phase difference in a rotation direction of said shaft relative to one another, and said die holes are disposed in correspondence with said plurality of punches,    wherein numbers of said plurality of punches in said plurality of punch trains are different from each other,    wherein one of said plurality of punch trains is selectively used in cutting holes in sheets, and    wherein after a sheet in which holes are cut by the one of said plurality of punch trains has passed, punches of another of said plurality of punch trains and die holes are engaged with one another without cutting holes in sheets in the predetermined sheet conveying interval.    
   
   
       14 . A sheet punching device according to  claim 13 , further comprising a sheet end detecting sensor, which detects an end of the sheet.  
   
   
       15 . A sheet punching device according to  claim 13 , further comprising an initial position detecting sensor, which detects an initial position of each of said plurality of punch trains in a rotation direction of said shaft, 
 wherein one of said plurality of punch trains selected for use is set at the initial position based on a signal from said initial position detecting sensor.    
   
   
       16 . A sheet punching device according to  claim 14 , wherein said sheet end detecting sensor detects a trailing end of the sheet, and one of said plurality of punch trains cuts holes in the sheet in the vicinity of the trailing end of the sheet.