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Browse Prior Art Database

FIRST PASS MULTIFEED DETECTION IN A DOCUMENT HANDLER

IP.com Disclosure Number: IPCOM000026966D
Original Publication Date: 1994-Aug-31
Included in the Prior Art Database: 2004-Apr-07
Document File: 4 page(s) / 213K

Publishing Venue

Xerox Disclosure Journal

Abstract

An apparatus and method for detecting a first pass multifeed error in a recirculating document handler is disclosed. A multifeed error is defined as feeding more than one original image bearing sheet to an imaging station in an automatic or recirculating document handler (RDH), and the like, of an electronic printing or copying machine. The apparatus is comprised of an electromagnetic brake located inside an imaging platen exit idler roller shaft which stops the roller momentarily, for example about 20 to 30 milliseconds, thereby allowing multifeeds to separate and causes the width of a sheet, as measured by sensors, to appear greater than expected and subsequently stops the document handler.

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Page 1 of 4

XEROX DISCLOSURE JOURNAL

FIRST PASS MULTIFEED Proposed Classification DETECTION IN A DOCUMENT
HANDLER
Int. C1. GOlj 03/30 Thomas Acquaviva

U.S. C1.355/317

FIG. 1

XEROX DISCLOSURE JOURNAL - Vol. 19, No. 4 July/August 1994 337

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Page 2 of 4

FIRST PASS MULTIFEED DETECTION IN A DOCUMENT HANDLER( Cont'd)

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338 XEROX DISCLOSURE JOURNAL - Vol. 19, No. 4 July/August 1994

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Page 3 of 4

FIRST PASS MULTIFEED DETECTION IN A DOCUMENT HANDLER( Cont'd)

An apparatus and method for detecting a first pass multifeed error in a recirculating document handler is disclosed. A multifeed error is defined as feeding more than one original image bearing sheet to an imaging station in an automatic or recirculating document handler (RDH), and the like, of an electronic printing or copying machine. The apparatus is comprised of an electromagnetic brake located inside an imaging platen exit idler roller shaft which stops the roller momentarily, for example about 20 to 30 milliseconds, thereby allowing multifeeds to separate and causes the width of a sheet, as measured by sensors, to appear greater than expected and subsequently stops the document handler.

Prior art teaches sensing or detecting multifeeds prior to imaging. The present system teaches the opposite sequence - image and then detect the multifeed. This is accomplished by separating the multifeed documents and thus detecting documents which are overly long, wide or both.

Current technology detects multifeeds by counting the number of document feeds until a set separator indicates an "end-of-set". This count is compared

with the count from the next pass. If the two counts differ, then a multifeed has occurred, either on the preceding or subsequent pass. The problem with this scheme is that when a multifeed is detected, at least two complete copy sets have already been made and one set contains missing pates. The recovery process usually involves discarding both sets and results in paper waste and user/operator dissatisfaction. Multifeeds can be an especially severe problem

with electronic document handlers, for example scanners, where only one pass is ever made and multifeed detection using counting can not be effectively used. Previous alternative attempts at first pass multifeed detection have included: measuring the thickness of succeeding sheets to compare if two or more sheets have been fed; monitoring sheet opacity or transmission; measuring sheet width to detect a shingle feed; and measuring sheet position relative to a vacuum orifice. These techniques may work with copy paper but fail with document handlers because the user/operator is permitted to load sheets of varying basis weight, beam support strength, opacity, image location, and the like.

A typical RDH with a feeder 1, platen transport 2, and platen exit nip 3 is shown in Figure 1. The width of ea...