Browse Prior Art Database

SKEW DETECTOR AND METHOD OF CORRECTION

IP.com Disclosure Number: IPCOM000025736D
Original Publication Date: 1987-Aug-31
Included in the Prior Art Database: 2004-Apr-04
Document File: 2 page(s) / 93K

Publishing Venue

Xerox Disclosure Journal

Abstract

In a skew detector as shown schematically in Figure 1, the paper is initially detected by roller B and then at a time dt later by roller A. If the separation of the rollers is d and the speed of the paper is v, the skew angle will be tan-1 (dt x

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XEROX DISCLOSURE JOURNAL

SKEW DETECTOR AND METHOD OF CORRECTION
Raymond W. Huggins

Proposed Classification

US. C1.355/14 Int. C1. G03g 15/00

IF REQUIRED

R MOT0 STEPPER 2 FIG MOTOR STEPPER w w

Volume 12 Number 4 July/August 1987 205

[This page contains 1 picture or other non-text object]

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SKEW DETECTOR AND METHOD OF CORRECTION (Cont'd)

In a skew detector as shown schematically in Figure 1, the paper is initially detected by roller B and then at a time dt later by roller A. If the separation of the rollers is d and the speed of the paper is v, the skew angle will be tan-1 (dt x

v i d). It follows that the precision of the measurement will increase as the distance between the two conducting rollers increases.

A method of easily quantifying the skew angle and correcting the paper orientation is shown in Figure 2. The shaft on which the two pinch rollers are mounted is split and each side is driven by a stepper motor. Separate idler rollers will also be required, and either the pinch or idler roller can be made of conducting rubber and be the paper presence detector. Normally, the stepper motors will be driven in synchronism and both rollers will be driven at the same speed.

When a piece of paper entering the two rollers is skewed, the time delay between the paper entering roller B and roller A can be found in terms of the number of stepper motor driving pulses say n. Control logic can then be arranged to increase the number of steps made by motor A, or dec...