Sheet reversing apparatus and image forming apparatus

Abstract

In a sheet reversing unit, an attraction belt is supported, in a 180° twisted position, between a belt driving roller at a conveying start position and a belt driving roller at a conveying end position, and a sheet is conveyed by providing the attraction belt with an electrostatic force from an AC power supply and thus by being attracted to the attraction belt, whereby the sheet is reversed.

1 . A sheet reversing apparatus for reversing a sheet by a predetermined angle, comprising: 
 a conveying belt for conveying a sheet;    drive means which drives the conveying belt; and    attraction means which causes the conveying belt to attract the sheet;    wherein a sheet attractive surface of the conveying belt has a twisting between a conveying start position and a conveying end position.    
   
   
       2 . A sheet reversing apparatus according to  claim 1 , wherein the conveying belt reverses a top side and a rear side of the sheet between the conveying start position and the conveying end position.  
   
   
       3 . A sheet reversing apparatus according to  claim 1 , wherein the conveying belt includes at least two conveying belts for conveying the sheet along a conveying direction thereof; and 
 a sum of twisting angles of the plural conveying belts is equal to an angle required for reversing a top side and a rear side of the sheet at the conveying start position.    
   
   
       4 . A sheet reversing apparatus according to  claim 1 , wherein the attraction means causes the conveying belt to attract the sheet by an electrostatic attraction.  
   
   
       5 . A sheet reversing apparatus according to  claim 4 , wherein the attraction means includes control means which controls an attractive force according to a type of the sheet.  
   
   
       6 . A sheet reversing apparatus according to  claim 1 , further comprising auxiliary separation means which separates the sheet, attracted to the conveying belt, from the conveying belt at the conveying end position.  
   
   
       7 . A sheet reversing apparatus for reversing a sheet by a predetermined angle, comprising: 
 a belt driving roller provided in a conveying start position of the sheet;    a belt driving roller provided in a conveying end position of the sheet;    an attraction belt supported in a state twisted by a predetermined angle between the belt driving rollers; and    a charging control portion for controlling an AC power supply or DC power supply to supply the belt driving rollers with a current thereby providing the attraction belt with an electrostatic force.    
   
   
       8 . A sheet reversing apparatus according to  claim 7 , further comprising a backup roller at an approximate center of the belt driving rollers and inside the supported attraction belt, in order to prevent a mutual friction of the attraction belt.  
   
   
       9 . A sheet reversing apparatus according to  claim 7 , wherein the charge control portion controls the attractive force of the attraction belt according to a type of the sheet.  
   
   
       10 . A sheet reversing apparatus according to  claim 7 , further comprising a charge eliminating needle for reducing the attractive force of the attraction belt in the vicinity of the conveying end position of the sheet, whereby the sheet attracted to the attraction belt is separated by the charge eliminating needle.  
   
   
       11 . A sheet reversing apparatus according to  claim 7 , further comprising a separating claw rotatably provided in the vicinity of the conveying end position of the sheet and contacted with the attraction belt by a spring, whereby the sheet attracted to the attraction belt is separated by the separating claw.  
   
   
       12 . An image forming apparatus comprising: 
 an image forming portion; and    a two-side conveying path for conveying a sheet, which bears, on a first side thereof, an image formed by the image forming portion, to the image forming portion again;    wherein the both-side conveying path includes a sheet reversing apparatus according to any one of  claims 1  to  11 .