Sheet processing apparatus and sheet processing method

Abstract

A sheet processing apparatus comprises a first conveyer roller pair and a second conveyer roller pair arranged on a sheet conveyance route along with a punch unit arranged between the first conveyer roller pair and the second conveyer roller pair. When it detects the tail end of a sheet of paper being conveyed in the direction from the first conveyer roller pair toward the second conveyer roller pair passing the first conveyer roller pair, it drives the second conveyer roller pair to rotate reversely and move the sheet of paper backward. Additionally, it causes a stopper to appear at a position defined by a predetermined distance of backward movement of the tail end of the sheet of paper and so as to make the sheet of paper abut the stopper and correct the skew, if any. After correcting the skew, it cuts a hole in the sheet of paper by means of the punch unit.

1 . A sheet processing apparatus for executing a hole cutting process on a sheet of paper carrying an image formed thereon, the apparatus comprising: 
 a sheet conveying section including a first conveyer roller pair and a second conveyer roller pair arranged on a sheet conveyance route and adapted to convey a sheet of paper along the conveyance route by the rotation of the first conveyor roller pair and that of the second conveyor roller pair;    a punch unit arranged between the first conveyer roller pair and the second conveyer roller pair and adapted to execute a hole cutting process on the sheet of paper;    a drive section that controls the rotary condition of the first conveyer roller pair and that of the second conveyer roller pair so as to convey the sheet of paper in the first direction from the first conveyer roller pair to the second conveyer roller pair or reversely in the second direction from the second conveyer roller pair to the first conveyer roller pair; and    a skew correcting section that drives the second conveyer roller pair to rotate reversely on the way of conveying the sheet of paper in the first direction after the time when the tail end of the sheet of paper passes the first conveyer roller pair to move the sheet of paper backward in the second direction, causing a stopper to appear at a position defined by a predetermined distance of backward movement of the sheet of paper so as to make the backwardly moving sheet of paper abut the stopper in order to correct, if any, of the skew of the sheet of paper;    the first conveyer roller pair and the second conveyer roller pair being so controlled as to convey the sheet of paper in the first direction after cutting a hole in the sheet of paper by the punch unit after correcting the skew, if any, thereof.    
   
   
       2 . The apparatus according to  claim 1 , wherein the first conveyer roller pair is made to operate as the stopper and adapted to pinch a sheet of paper between the rollers of the pair and convey it; and 
 the skew correcting section stops the rotary motion of the first roller pair and makes the backwardly moving sheet of paper abut the first conveyer roller pair in order to correct the skew, if any, of the sheet of paper when the sheet of paper is driven to move backward.    
   
   
       3 . The apparatus according to  claim 1 , wherein 
 the stopper of the skew correcting section is formed by a shutter adapted to project across the route of backward movement of the sheet of paper in the second direction and the shutter is driven to project across the conveyance route so as to make the sheet of paper abut the shutter in order to correct the skew, if any, of the sheet of paper when the sheet of paper is driven to move backward.    
   
   
       4 . The apparatus according to  claim 3 , wherein 
 the shutter is adapted to be driven by a drive motor so as to retractably project across the route of backward movement of the sheet of paper in the second direction.    
   
   
       5 . The apparatus according to  claim 1 , further comprising: 
 a sensor that detects the tail end of the sheet of paper being conveyed in the first direction and passing the first conveyer roller pair and a backward movement of the sheet of paper in the second direction, wherein the skew correcting section controls the drive section by using the outcome of the detecting operation of the sensor and controls the rotary condition of the first conveyer roller pair and that of the second roller pair.    
   
   
       6 . The apparatus according to  claim 1 , wherein 
 the second conveyer roller pair is adapted to pinch a sheet of paper between the rollers of the pair and convey it; and    the skew correcting section causes the rollers of the second conveyer roller pair to lightly contact with each other and operate as slipping rollers when conveying the sheet of paper in the second direction.    
   
   
       7 . The apparatus according to  claim 1 , wherein 
 the hole cutting position of the sheet of paper is determined by the gap between a hole cutting blade of the punch unit and the stopper; and    the punch unit is adapted to execute a hole cutting process near the tail end of the sheet of paper corrected for the skew, if any.    
   
   
       8 . The apparatus according to  claim 7 , wherein 
 the gap L 2  between the hole cutting position by the punch unit and the stopper is defined to be L 2 ≈L 1 , where L 1  is the gap between the tail end of the sheet of paper and the hole cutting position.    
   
   
       9 . A sheet processing apparatus for executing a hole cutting process on a sheet of paper carrying an image formed thereon, the apparatus comprising: 
 a sheet conveying section including a first conveyer roller pair and a second conveyer roller pair arranged on a sheet conveyance route and adapted to convey a sheet of paper along the conveyance route by the rotation of the first conveyor roller pair and that of the second conveyor roller pair;    a punch unit arranged between the first conveyer roller pair and the second conveyer roller pair and adapted to execute a hole cutting process on the sheet of paper;    a drive section that controls the rotary condition of the first conveyer roller pair and that of the second conveyer roller pair so as to convey the sheet of paper in the first direction from the first conveyer roller pair to the second conveyer roller pair or reversely in the second direction from the second conveyer roller pair to the first conveyer roller pair;    a skew correcting section that drives the second conveyer roller pair to rotate reversely on the way of conveying the sheet of paper in the first direction after the time when the tail end of the sheet of paper passes the first conveyer roller pair to move the sheet of paper backward in the second direction, causing a stopper to appear at a position defined by a predetermined distance of backward movement of the sheet of paper so as to make the backwardly moving sheet of paper abut the stopper in order to correct, if any, of the skew of the sheet of paper; and    a control section including detection means for detecting the position of the sheet of paper on the conveyance route and adapted to control the rotary condition of the first conveyer roller pair and that of the second conveyer roller pair, the appearance of the stopper and the punching process of the punch unit in response to the outcome of the detection means;    the sheet of paper corrected for the skew, if any, being subjected to a hole cutting process and delivered.    
   
   
       10 . The apparatus according to  claim 9 , further comprising: 
 a sensor arranged in close proximity of the first conveyer roller pair to detect the position of the sheet of paper on the conveyance route.    
   
   
       11 . A sheet processing method comprising: 
 arranging a first conveyer roller pair and a second conveyer roller pair on a sheet conveyance route and a punch unit between the first conveyer roller pair and the second conveyer roller pair for executing a hole cutting process on the sheet of paper;    controlling the rotary condition of the first conveyer roller pair and that of the second conveyer roller pair so as to convey the sheet of paper in the first direction from the first conveyer roller pair to the second conveyer roller pair;    reversing the sense of rotation of the second conveyer roller pair to drive the sheet of paper to move backward reversely in the second direction from the second conveyer roller pair to the first conveyer roller pair on the way of conveying the sheet of paper in the first direction at the time when the tail end of the sheet of paper passes the first conveyer roller pair;    causing a stopper to appear at a position defined by a predetermined distance of backward movement of the sheet of paper so as to make the backwardly moving sheet of paper abut the stopper in order to correct, if any, of the skew of the sheet of paper;    cutting a hole in the sheet of paper by means of the punch unit after correcting the skew, if any, thereof; and    controlling the sense of rotation of the first conveyer roller pair and that of the second conveyer roller pair so as to convey the sheet of paper in the first direction after cutting a hole in the sheet of paper.    
   
   
       12 . The method according to  claim 11 , wherein 
 the first conveyer roller pair is made to operate as the stopper and adapted to pinch a sheet of paper between the rollers of the pair and convey it; and    the rotary motion of the roller pair is stopped and the backwardly moving sheet of paper is made abut the first conveyer roller pair in order to correct the skew, if any, of the sheet of paper when the sheet of paper is driven to move backward in the second direction.    
   
   
       13 . The method according to  claim 11 , wherein 
 the stopper is formed by a shutter adapted to project across the route of backward movement of the sheet of paper in the second direction and the shutter is driven to project across the conveyance route so as to make the sheet of paper abut the shutter in order to correct the skew, if any, of the sheet of paper when the sheet of paper is driven to move backward.    
   
   
       14 . The method according to  claim 13 , wherein 
 the shutter is adapted to be driven by a drive motor and made to project across the route of backward movement of the sheet of paper in the second direction when correcting the skew, if any.    
   
   
       15 . The method according to  claim 11 , wherein 
 the second conveyer roller pair is adapted to pinch the sheet of paper between the rollers of the pair and convey it; and    the rollers of the second conveyer roller pair are caused to lightly contact with each other and operate as slipping rollers when conveying the sheet of paper in the second direction at the time of correcting the skew, if any.