Double feeding detection apparatus, auto sheet feeder and double feed detection method

Abstract

A double feed detection apparatus includes a first element and a second element at positions where they are opposite to each other across a sheet, and a direction in which an ultrasonic wave or a light passes through the sheet is vertical to a conveyance direction of the sheet. An auto sheet feeder includes the first element and the second element of the double feed detection apparatus in a range from a downstream side of a joining point of an outside conveyance path and an inside conveyance path in the sheet conveyance direction to a near side of a read part.

1 . A double feed detection apparatus comprising:
 a control section to generate a control signal;   a transmission signal generation section to generate a transmission signal from the control signal of the control section;   a transmission amplifying section to amplify the transmission signal;   a first element to output the amplified signal to a sheet in a direction perpendicular to a conveyance direction of the sheet;   a second element to receive the signal of the first element passing through the sheet;   a reception amplifying section to amplify the received signal; and   an A/D converter to convert the received signal as the amplified analog signal into a digital signal and to output it to the control section.   
     
     
         2 . The apparatus of  claim 1 , wherein the first element is a first ultrasonic element and the second element is a second ultrasonic element. 
     
     
         3 . The apparatus of  claim 2 , wherein the first ultrasonic element and the second ultrasonic element are provided to have an ultrasonic wave incident angle of 40° or less with respect to a surface of the sheet. 
     
     
         4 . The apparatus of  claim 3 , further comprising a changeover switch, wherein when the first ultrasonic element is connected to the transmission amplifying section, the second ultrasonic element is connected to the reception amplifying section, and when the second ultrasonic element is connected to the transmission amplifying section, the first ultrasonic element is connected to the reception amplifying section. 
     
     
         5 . The apparatus of  claim 1 , wherein the first element is a light emitting element, and the second element is a light receiving element. 
     
     
         6 . The apparatus of  claim 5 , wherein the light emitting element and the light receiving element are provided to have a light incident angle of 90° or less with respect to a surface of the sheet. 
     
     
         7 . An auto sheet feeder comprising:
 a paper feed tray on which documents to be read are placed;   a pickup roller to take out a sheet one by one from the paper feed tray and to deliver it to a conveyance mechanism;   the conveyance mechanism which includes an outside conveyance path and an inside conveyance pat, receives the sheet from the pickup roller and conveys it;   a front surface read section to read a front surface of the sheet;   a rear surface read section to read a rear surface of the sheet;   a storage tray on which the read sheet is stacked;   a control section to generate a control signal;   a transmission signal generation section to generate a transmission signal from the control signal of the control section;   a transmission amplifying section to amplify the transmission signal;   a first element to output the amplified signal to the sheet in a direction perpendicular to a conveyance direction of the sheet;   a second element to receive the signal of the first element passing through the sheet;   a reception amplifying section to amplify the received signal; and   an A/D converter to convert the received signal as the amplified analog signal into a digital signal and to output it to the control section.   
     
     
         8 . The feeder of  claim 7 , wherein the first element is a first ultrasonic element and the second element is a second ultrasonic element. 
     
     
         9 . The feeder of  claim 8 , wherein the first ultrasonic element and the second ultrasonic element are provided to have an ultrasonic wave incident angle of 40° or less with respect to a surface of the sheet. 
     
     
         10 . The feeder of  claim 9 , further comprising a changeover switch, wherein when the first ultrasonic element is connected to the transmission amplifying section, the second ultrasonic element is connected to the reception amplifying section, and when the second ultrasonic element is connected to the transmission amplifying section, the first ultrasonic element is connected to the reception amplifying section. 
     
     
         11 . The feeder of  claim 7 , wherein the first element is a light emitting element, and the second element is a light receiving element. 
     
     
         12 . The feeder of  claim 11 , wherein the light emitting element and the light receiving element are provided to have alight incident angle of 90° or less with respect to a surface of the sheet. 
     
     
         13 . The feeder of  claim 7 , wherein the first element and the second element are provided in a range from a downstream side of a joining point of the outside conveyance path and the inside conveyance path in the sheet conveyance direction to a near side of a read part. 
     
     
         14 . The feeder of  claim 7 , wherein when one of an OUT sheet passing sensor to detect passing of the sheet along the outside conveyance path and an IN sheet passing sensor to detect passing of the sheet along the inside conveyance path is damaged to be ON, the conveyance path having the damaged sensor is not used, and the sheet is conveyed to only the conveyance path having the normal sensor. 
     
     
         15 . The feeder of  claim 7 , wherein when one of an OUT sheet passing sensor to detect passing of the sheet along the outside conveyance path and an IN sheet passing sensor to detect passing of the sheet along the inside conveyance path is damaged to be OFF, the conveyance path where a jam occurs continuously is not used, and the sheet is conveyed to only the normal conveyance path. 
     
     
         16 . A double feed detection method comprising:
 generating a control signal by a control section;   generating a transmission signal from the control signal by a transmission signal generation section;   amplifying the transmission signal by a transmission amplifying section;   outputting the amplified signal to a sheet in a direction perpendicular to a conveyance direction of the sheet by a first element;   receiving the signal of the first element passing through the sheet by a second element;   amplifying the received signal by a reception amplifying section; and   converting the received signal as the amplified analog, signal into a digital signal by an A/D converter and outputting it to the control section.   
     
     
         17 . The method of  claim 16 , wherein the first element is a first ultrasonic element and the second element is a second ultrasonic element. 
     
     
         18 . The method of  claim 17 , wherein the first ultrasonic element and the second ultrasonic element are provided to have an ultrasonic wave incident angle of 40° or less with respect to a surface of the sheet. 
     
     
         19 . The method of  claim 18 , wherein a changeover switch is used and when the first ultrasonic element is connected to the transmission amplifying section, the second ultrasonic element is connected to the reception amplifying section, and when the second ultrasonic element is connected to the transmission amplifying section, the first ultrasonic element is connected to the reception amplifying section. 
     
     
         20 . The method of  claim 16 , wherein
 the first element is a light emitting element,   the second element is a light receiving element, and   the light emitting element and the light receiving element are provided to have a light incident angle of 90° or less with respect to a surface of the sheet.