Double document detection system

• US 4,243,216 A
• Filed: 06/11/1979
• Issued: 01/06/1981
• Est. Priority Date: 06/11/1979
• Status: Expired due to Term

• Current Assignee: NCR Corporation
• Original Assignee: NCR Corporation
• Inventors: Mazumder, Ali T.
• Primary Examiner(s): Stoner, Jr., Bruce H.
• Application Number:
  US06/047,460
• Time in Patent Office: 575 Days
• Field of Search: 271/263, 271/262, 340/562, 340/674, 324/61 R, 209/571, 209/572, 209/603, 33/143 L, 33/147 N, 33/148 N
• US Class Current: 271/263
• CPC Class Codes: G06K 13/067 Checking presence, absence, correct position, or moving status of cards

Abstract

A system for detecting the presence of more than one document along a path during the processing of the documents. A capacitance is introduced by the plural documents in contact with each other and wherein a delay signal is combined with an original signal to generate a multiple document detect signal for indicating the presence of the multiple documents.

Claims

1. A double document detector comprising a

conductive capacitor type sensing device operable for utilizing a document as the dielectric thereof and for generating a signal upon physically detecting a document,

first R-C circuit means for introducing a capacitive delay in the generated signal due to the presence of one or more documents,

AND gate means for comparing the generated signal with the delayed signal and generating an output signal,

second R-C circuit means for introducing a capacitive delay in the output signal of said AND gate means to compensate for capacitance other than capacitance due to the presence of two or more documents, and

inverter means receiving said delayed output signal from said AND gate means for generating a multiple document signal upon the presence of capacitive delay indicating that more than one document has been detected by said sensing device.

2. In a document handling apparatus, means for detecting the passage of double documents along a path comprising a

conductive capacitor type sensing device operable for utilizing a document as the dielectric thereof and for generating a signal upon physically detecting a document,

first R-C circuit means for introducing a delay in the generated signal due to the presence of a document,

AND gate means for comparing the generated signal with the delayed signal and generating an output signal,

second R-C circuit means for introducing a capacitive delay in the output signal of said AND gate means to compensate for capacitance other than capacitance due to the presence of two or more documents,

and means receiving said delayed output signal from said AND gate means for generating a double document signal when said delayed output signal indicates that more than one document is detected by said sensing device.

3. A method of detecting double documents comprising the steps of:

generating a signal upon physically detecting a document,

introducing a capacitive delay in the generated signal due to presence of one or more documents,

inverting the generated signal delayed due to presence of more than one document,

comparing the generated signal with the delayed signal to generate and output signal,

introducing a capacitive delay in the output signal to compensate for capacitance other than capacitance due to the presence of two or more documents, and

generating a double document signal when the delayed output signal indicates that more than one document is detected.