Postprocessing apparatus and image forming apparatus

Abstract

A processing unit performs a postprocess for a sheet bunch on a processing tray. In a waiting transportation path, a subsequent sheet can wait while the postprocess is performed for the sheet bunch. If sheet transportation is suspended, a controller determines whether concurrent transportation is performed or not on the basis of whether there is the sheet bunch on the processing tray and whether there is the subsequent sheet in the waiting transportation path. In the concurrent transportation, when the sheet bunch is outputted through an ejection port, the controller transports the subsequent sheet to an output roller and causes the subsequent sheet to protrude from the ejection port such that the subsequent sheet partially overlaps the sheet bunch, and after a rear end of the sheet bunch passes through the ejection port, the controller reverses the output roller and transports the subsequent sheet to the processing tray.

What is claimed is: 
     
         1 . A postprocessing apparatus configured to perform a postprocess for a sheet bunch of a sheet transported from a previous-stage device, comprising:
 a processing unit configured to perform the postprocess for the sheet bunch on a processing tray;   an output roller configured to output the sheet bunch after the postprocess through an ejection port;   a waiting transportation path in which a subsequent sheet can wait while the postprocess is performed for the sheet bunch;   a transportation roller configured to draw the subsequent sheet to the waiting transportation path and transport the subsequent sheet from the waiting transportation path to the processing tray; and   a controller configured to control the processing unit, the output roller, and the transportation roller;   wherein if transportation of a sheet is suspended, the controller determines whether concurrent transportation is performed or not on the basis of (a) whether there is the sheet bunch on the processing tray or not and (b) whether there is the subsequent sheet in the waiting transportation path or not; and   in the concurrent transportation, (a) when the sheet bunch is outputted through the ejection port, the controller controls the transportation roller and thereby transports the subsequent sheet to the output roller and causes the subsequent sheet to protrude from the ejection port such that the subsequent sheet partially overlaps the sheet bunch, and (b) after a rear end of the sheet bunch passes through the ejection port, the controller reverses the output roller and transports the subsequent sheet to the processing tray.   
     
     
         2 . The postprocessing apparatus according to  claim 1 , wherein if there is the sheet bunch on the processing tray and there is the subsequent sheet in the waiting transporting path when the transportation is suspended, then the controller performs the concurrent transportation. 
     
     
         3 . The postprocessing apparatus according to  claim 1 , wherein if there is not the sheet bunch on the processing tray and there is the subsequent sheet in the waiting transporting path when the transportation is suspended, then the controller does not perform the concurrent transportation and controls the transportation roller and thereby immediately transports the subsequent sheet to the processing tray. 
     
     
         4 . The postprocessing apparatus according to  claim 3 , wherein when the transportation is resumed after suspended, the controller controls the transportation roller and thereby does not transport a sheet incoming when the transportation is resumed to the waiting transportation path but transports the sheet to the processing tray. 
     
     
         5 . The postprocessing apparatus according to  claim 1 , wherein if there is the sheet bunch on the processing tray and there is not the subsequent sheet in the waiting transporting path when the transportation is suspended, then the controller does not perform the concurrent transportation and (a) determines whether the postprocess has been performed for the sheet bunch on the processing tray or not, (b1) if the postprocess has been performed for the sheet bunch on the processing tray, controls the output roller and thereby immediately outputs the sheet bunch to the ejection port, and (b2) if the postprocess has not been performed for the sheet bunch on the processing tray, does not perform immediate output of the sheet bunch. 
     
     
         6 . An image forming apparatus, comprising:
 a postprocessing apparatus configured to perform a postprocess for a sheet bunch of a sheet transported from a previous-stage device; and   an image forming apparatus main body as the previous-stage device;   wherein the postprocessing apparatus comprises:
 a processing unit configured to perform the postprocess for the sheet bunch on a processing tray; 
 an output roller configured to output the sheet bunch after the postprocess through an ejection port; 
 a waiting transportation path in which a subsequent sheet can wait while the postprocess is performed for the sheet bunch; 
 a transportation roller configured to draw the subsequent sheet to the waiting transportation path and transport the subsequent sheet from the waiting transportation path to the processing tray; and 
 a controller configured to control the processing unit, the output roller, and the transportation roller; 
 wherein if transportation of a sheet is suspended, the controller determines whether concurrent transportation is performed or not on the basis of (a) whether there is the sheet bunch on the processing tray or not and (b) whether there is the subsequent sheet in the waiting transportation path or not; and 
 in the concurrent transportation, (a) when the sheet bunch is outputted through the ejection port, the controller controls the transportation roller and thereby transports the subsequent sheet to the output roller and causes the subsequent sheet to protrude from the ejection port such that the subsequent sheet partially overlaps the sheet bunch, and (b) after a rear end of the sheet bunch passes through the ejection port, the controller reverses the output roller and transports the subsequent sheet to the processing tray.