The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Oct. 08, 1991
Filed:
Sep. 17, 1990
Douglas L Milne, Dundee, GB;
NCR Corporation, Dayton, OH (US);
Abstract
A document sensing apparatus includes a phototransistor (12) for generating a first or second voltage depending on whether or not, respectively, a document is present at a sensing location, and a capacitor (36) for providing a second voltage whose peak value is determined by said second value. A voltage comparator (30, 38, 40) compares said first and second voltages and provides an output signal indicative of the presence of a document at the sensing location if said first voltage is less than a predetermined fraction of said second voltage. A microprocessor (44) controls the operation of a circuit (71-1) which provides, as necessary, a charging current to said capacitor (36) so that, while a document is present at the sensing location, said second voltage is prevented from falling by a significant amount, thereby preventing problems occurring if a document remains at the sensing location for a prolonged period due to a feeding irregularity.