Browse Prior Art Database

Double Document Detect System

IP.com Disclosure Number: IPCOM000088304D
Original Publication Date: 1977-May-01
Included in the Prior Art Database: 2005-Mar-04
Document File: 2 page(s) / 48K

Publishing Venue

IBM

Related People

Boothroyd, WA: AUTHOR

Abstract

This article describes an apparatus, including a circuit, for detecting a double-feed error in a document transport mechanism. The current supplied to an illuminating lamp is adjusted to keep the output of the cooperating photocell constant with respect to a reference voltage over the long time period. A short term drop in the output of the photocell is interpreted as the detection of one or more documents. Further, the output signal during this "drop" is processed to establish whether one or more documents are present.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 53% of the total text.

Page 1 of 2

Double Document Detect System

This article describes an apparatus, including a circuit, for detecting a double-feed error in a document transport mechanism. The current supplied to an illuminating lamp is adjusted to keep the output of the cooperating photocell constant with respect to a reference voltage over the long time period. A short term drop in the output of the photocell is interpreted as the detection of one or more documents. Further, the output signal during this "drop" is processed to establish whether one or more documents are present.

Referring to the figures, the output of photocell 1 is fed to current-to-voltage converter 2 and then to comparator 3, document detector 4, and inverting amplifier 5. Reference voltage 9 provides voltages to comparator 3 and document detector 4 which are constant with respect to time, and through variable resistor 20 a constant set-point voltage to summing circuit 6. The output of document detector 4 is fed to presettable integrator circuit 7, while the output of sum circuit 6 is fed to integrator 7. The output of integrator 7 is compared in comparator 8 with ground, and the output of comparator 8 appears as the double document signal. The output of comparator 3 is integrated at delay circuit 10, the output of which is fed to current regulator 11 for driving lamp 12. The output of lamp 12 is focused through diffusion layer 13 upon photocell 1.

A document is driven along the transport path between serpentine belts 16 which are driven by serpentine rollers 17 and 18. Lamp 12 is mounted to mounting bracket 14, and photocell 1 to mounting bracket 15. Bristle brush 19 sprin...