Multiple sheet detection system

Abstract

A multiple feed document detection system for use with a document transport for detecting the presence of multiple documents utilizes multiple doubles detection devices wherein each device detects the presence of doubles. The output signals of each device are applied to a comparator which compares the signals obtained from each device. If each device indicates the presence of doubles, then the comparator provides an output that multiple sheets are present. The system thereby eliminates the reading of false doubles by the comparison of the output signals from two or more doubles detection devices.

1 . A system for detecting the presence of multiple sheets moving along a path, the system comprising: 
 a first doubles detection device disposed at a first position along the path, said first doubles detection device generating a first output signal upon detection of multiple sheets and a second output signal upon detection of a single sheet at the first position;    a second doubles detection device disposed at a second position along the path, said second doubles detection device generating a first output signal upon detection of multiple sheets and a second output signal upon the detection of a single sheet at the second position; and    a comparator for receiving said output signals of said first and said second doubles detection devices and for generating an output signal indicating the presence of multiple documents along the path when said first output signal of said first doubles detection device and said first output signal of said second doubles detection device are present.    
   
   
       2 . The system of  claim 1  wherein said first doubles detection device includes an ultrasonic detection device.  
   
   
       3 . The system of  claim 2  wherein said second doubles detection device includes a clutch and roller detection device.  
   
   
       4 . The system of  claim 2  wherein said second doubles detection device includes a thickness detection device.  
   
   
       5 . The system of  claim 2  wherein said second doubles detection device includes a vacuum detection device.  
   
   
       6 . A system for detecting the presence of multiple sheets moving along a path, the system comprising: 
 an ultrasonic detection device disposed at a first position along the path, said ultrasonic doubles detection device generating a first output signal upon detection of multiple sheets and a second output signal upon detection of a single sheet at the first position;    a first doubles detection device disposed at a second position along the path, said first doubles detection device generating a first output signal upon detection of multiple sheets and a second output signal upon detection of a single sheet at the second position;    a second doubles detection device disposed at a third position along the path, said second doubles detection device generating a first output signal upon detection of multiple sheets and a second output signal upon the detection of a single sheet at the third position; and    a comparator for receiving said output signals of said ultrasound detection device and said first and said second doubles detection devices and for generating an output signal indicating the presence of multiple documents along the path when said first output signals of said doubles detection devices are present.    
   
   
       7 . The system of  claim 6  wherein said first doubles detection device includes a thickness detection device and said second doubles detection device includes a clutch and roller detection device.  
   
   
       8 . The system of  claim 6  wherein said first doubles detection device includes a thickness detection device and said second doubles detection device includes a vacuum detection device.  
   
   
       9 . The system of  claim 6  wherein said first doubles detection device includes a clutch and roller detection device and said second doubles detection device includes a vacuum detection device.