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SENSING SCHEME TO DETECT INTERMIXED SIZE SHEETS

IP.com Disclosure Number: IPCOM000027372D
Original Publication Date: 1996-Jun-30
Included in the Prior Art Database: 2004-Apr-07
Document File: 4 page(s) / 150K

Publishing Venue

Xerox Disclosure Journal

Abstract

Document scanners often utilize a top feeder and must be able to detect the original size before it completely leaves the feed tray. If the size of the sheet is known in advance of scanning the document, the appropriate paper feed tray could be selected, and an auto-magnification feature could be enabled. For example, the tray of such a feeder can hold intermixed sizes, including 11" x 17", 14" x 8-1/2", 8-1/2" x 11

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XEROX DISCLOSURE JOURNAL

SENSING SCHEME TO DETECT INTERMIXED SIZE SHEETS Thomas Acquaviva

Proposed Classification
U. S. C1.355/311
Int. C1. G03g 21/00

FIGm 1

28

FIGm 2

XEROX DISCLOSURE JOURNAL - Vol. 21, No. 3 May/June 1996 237

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SENSING SCHEME TO DETECT INTERMIXED SIZE SHEETS (CONT'D)

Document scanners often utilize a top feeder and must be able to detect the original size before it completely leaves the feed tray. If the size of the sheet is known in advance of scanning the document, the appropriate paper feed tray could be selected, and an auto- magnification feature could be enabled. For example, the tray of such a feeder can hold intermixed sizes, including 11" x 17", 14" x 8-1/2", 8-1/2" x 11 'I, and 8-1/2" x 5-1/2". However, to sense the sizes of various documents in an intermixed set, well-known optical sensors looking at the stack lengths would not work because they could not distinguish which sheet is being fed. All they could do is detect the length of the longest sheet in the tray. Moreover, it is often impossible to measure the length of the document sheet as it travels to the imaging station because the paper path is too short; the lead edge is in the scanning station while the trail edge is still in the feed tray. What is required is a sensor that can detect the length of the sheet that is about to be fed.

Accordingly, rather than detect the length of a sheet, the proposed sensing scheme detects motion of the upper most sheet in the stack and infers its length. As illustrated schematically in Figure 1, four very lightly loaded, high fiiction wheels 10, 12, 14, and 16 rest on the top of document stack 20 at or near the four possible paper length positions
(e.g., 16", 13", lo", 5-1/2"). As shown in Figure 2, axle 24 of each wheel is, in turn,
operatively connected to an encoder disk 26 by any motion transferring mechanism, such as a belt, band, chain, etc. Sensor 28 detects the motion of encoder disk 26 in response to the motion of top sheet 8 being fed by fdretard roll 18 and produces a signal indicative thereof. The signals are fed to a microcontroller or similar analytic circuitry which in effect determines which of the fiiction wheels are turning. The paper lengths can then be inferred with the help of the following look-up table:

Sensor detecting motion Length of top sheet

D 5-1/2"

C+D 1 1 B+C+D 14" A+B+C+D 17"

At the same time, a document tray width guide will be attached to sensors which detect one of two possible paper widths; 8-1/2" or 11 If. Legal, 8-1/2" x 11 *I, and stateme...