Sheet processing apparatus

Abstract

A sheet processing apparatus includes a sheet-table unit, a sheet-separating unit, a convey unit, a discharge unit, a sheet processing unit, and a sensor arranged at an upstream end of the convey unit and spaced from the discharge unit with a predetermined distance. The convey unit has a convey roller, a convey pulley, and an elastic device connected with the convey pulley. The elastic device has a cylinder, a fixing shaft fixed to the cylinder, and a spring having two free ends fixed to the fixing shaft and a portion of the convey pulley opposite to the convey roller. When the signal resulted from a rear end of the sheet apart from the sensor is sent to the system controller, the cylinder is commanded by the system controller to draw back the fixing shaft. The spring is elongated to make the convey pulley away from the convey roller.

1 . A sheet processing apparatus adapted for processing a plurality of sheets, comprising:
 a sheet-table unit for holding the sheets;   a sheet-separating unit disposed at a downstream end of the sheet-table unit along a convey direction of the sheets, for separating the sheets one by one and feeding the sheets downstream;   a convey unit arranged at a downstream end of the sheet-separating unit along the convey direction of the sheets, for feeding the sheets downstream, the convey unit having a convey roller, a convey pulley detachably resting against the convey roller, and an elastic device connected with the convey pulley, the elastic device having a cylinder, a fixing shaft having one end fixed to the cylinder, and a spring having two free ends fixed to the other end of the fixing shaft and a portion of the convey pulley opposite to the convey roller;   a discharge unit located at a downstream end of the convey unit along the convey direction of the sheets, for discharging the sheets;   a sheet processing unit placed between the convey unit and the discharge unit, and close to a convey path of the sheets, for processing the sheets; and   a sensor arranged at an upstream end of the convey unit and spaced away from the discharge unit with a predetermined distance, for detecting the sheets and sending signals to a system controller;   wherein the convey pulley is forced by the spring to rest against the convey roller resiliently for conveying the sheet, when the signal resulted from a rear end of the sheet apart from the sensor is sent to the system controller, the cylinder is commanded by the system controller to draw back the fixing shaft, the spring is accordingly elongated to make the convey pulley away from the convey roller for releasing the conveying sheet.   
     
     
         2 . The sheet processing apparatus as set forth in  claim 1 , wherein the system controller drives the convey roller to rotate when the system controller receives the signal resulted from the sensor detecting a front end of the sheet. 
     
     
         3 . The sheet processing apparatus as set forth in  claim 2 , wherein the discharge unit has a discharge roller and a discharge pulley disposed against the discharge roller, the system controller controls the discharge roller to rotate when the system controller receives the signal resulted from the sensor detecting a front end of the sheet. 
     
     
         4 . The sheet processing apparatus as set forth in  claim 3 , further comprising a driving device which is commanded by the system controller to drive the convey roller and the discharge roller to rotate. 
     
     
         5 . The sheet processing apparatus as set forth in  claim 1 , wherein the sheet-separating unit has a separating roller and a retard roller disposed against the separating roller. 
     
     
         6 . The sheet processing apparatus as set forth in  claim 5 , further comprising a first driving device which is commanded by the system controller to drive the separating roller to rotate for feeding the sheets. 
     
     
         7 . The sheet processing apparatus as set forth in  claim 1 , wherein the elastic device further has a barrel surrounding the spring.