Sheet takeout device

Abstract

A sheet takeout mechanism has a takeout roller that rotates in contact with a sheet located at a takeout position, and a motor that intermittently rotates the takeout roller. A triangular suction port is formed on a suction surface of the takeout roller and has a vertex located downstream in a rotation direction of the takeout roller. When a negative pressure is exerted on the sheet via the suction port, the suction force is weak at the beginning of suction and then increases gradually.

1 . A sheet taking-out device comprising:
 a rotating member having a suction surface which travels along a sheet fed to a takeout position and a suction port formed on the suction surface;   a rotating mechanism which intermittently rotates the rotating member so as to minimize a rotation speed at a timing when the suction port passes by a suction position where the suction port sucks the sheet located at the takeout position;   a suction mechanism which allows the suction surface to generate a negative pressure via the suction port so that the sheet located at the takeout position is sucked by and contacted with the suction surface when the suction port passes by the suction position; and   suction force adjusting means which adjusts a suction force applied to the sheet located at the takeout position via the suction port so as to prevent the sheet from being sucked and moved by the suction surface while the suction port is approaching the suction position with the rotation speed of the rotating member reduced.   
   
   
       2 . The sheet takeout device according to  claim 1 , wherein the suction force adjusting means adjusts the suction force such that the sheet located at the takeout position is sucked by and contacted with the suction surface at a timing when the rotation speed of the rotating member is minimized to locate the suction port opposite the sheet. 
   
   
       3 . The sheet takeout device according to  claim 2 , wherein the suction force adjusting means adjusts the shape of the suction port such that a downstream aperture area of the suction port is smaller than an upstream aperture area of the suction port in a rotation direction of the rotating member. 
   
   
       4 . The sheet takeout device according to  claim 3 , wherein the suction port is formed to be a triangle having a vertex located downstream in the rotation direction of the rotating member. 
   
   
       5 . The sheet takeout device according to  claim 1 , wherein the suction force adjusting means controls the suction mechanism such that as the suction port approaches the suction position, the suction force applied via the suction port to the sheet located at the takeout position increases gradually. 
   
   
       6 . The sheet takeout device according to  claim 5 , wherein the suction force adjusting means has a valve which turns on and off the negative pressure and a controller which controls a switching timing for the valve so as to maximize the suction force at the timing when the suction port stands opposite the sheet located at the takeout position. 
   
   
       7 . The sheet takeout device according to  claim 2 , wherein the suction force adjusting means adjusts the shape of the suction port such that the downstream aperture area of the suction port is smaller than the upstream aperture area of the suction port in the rotation direction of the rotating member, and controls the suction mechanism such that as the suction port approaches the suction position, the suction force applied via the suction port to the sheet located at the takeout position increases gradually. 
   
   
       8 . The sheet takeout device according to  claim 7 , wherein the suction port is formed to be a triangle having a vertex located downstream in the rotation direction of the rotating member. 
   
   
       9 . The sheet takeout device according to  claim 7 , wherein the suction force adjusting means has a valve which turns on and off the negative pressure and a controller which controls a switching timing for the valve so as to maximize the suction force at the timing when the suction port stands opposite the sheet located at the takeout position. 
   
   
       10 . The sheet takeout device according to  claim 2 , wherein the rotating member is a substantially cylindrical takeout roller formed of a rigid body such as metal and having the suction surface on an outer periphery. 
   
   
       11 . The sheet takeout device according to  claim 2 , wherein the rotating member is an endless takeout belt wound and extended around a plurality of rollers.