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MAINTAINING CONSTANT PITCH WITH VARIABLE RETRACE TIME

IP.com Disclosure Number: IPCOM000024212D
Original Publication Date: 1979-Dec-31
Included in the Prior Art Database: 2004-Apr-02
Document File: 2 page(s) / 68K

Publishing Venue

Xerox Disclosure Journal

Abstract

Timing of copiers may be conveniently based on an interval of constant length. A typical pitch interval may, for example, be one copy/sec. In copiers of the scanning type wherein the document to be copied rests on a stationary platen while the scanning assembly moves therepast, retrace time of the scanning assembly, i.e., the time required for the scanning assembly to return to the start of scan position for the next copy, may, however, vary by as much as 200 msec. making it difficult to time copier operations on the basis of a constant or fixed pitch interval. Variations of this type in retrace time may be due to the fact that since scan length changes with changes in copy size, the length of the retrace stroke will also change. Also, as the copier is operated, scan carriage motor temperatures may increase with consequent change in the speed with which the scanning assembly is returned to start of scan position.

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CEROX DISCLOSURE JOURNAL

MAINTAINING CONSTANT PITCH WITH VARIABLE RETRACE TIME
Stephen P. Wilczek

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

Timing of copiers may be conveniently based on an interval of constant length. A typical pitch interval may, for example, be one copy/sec. In copiers of the scanning type wherein the document to be copied rests on a stationary platen while the scanning assembly moves therepast, retrace time of the scanning assembly, i.e., the time required for the scanning assembly to return to the start of scan position for the next copy, may, however, vary by as much as 200 msec. making it difficult to time copier operations on the basis of a constant or fixed pitch interval. Variations of this type in retrace time may be due to the fact that since scan length changes with changes in copy size, the length of the retrace stroke will also change. Also, as the copier is operated, scan carriage motor temperatures may increase with consequent change in the speed with which the scanning assembly is returned to start of scan position.

To assure accurate timing despite variations in scanning assembly retrace time, at the outset a dummy scan is run and retrace time from the dummy scan measured. On the first copy scan, -software (knowing the machine pitch interval and scan retrace time from the dummy scan) calculates the point at which retrace must start in order to assure that retrace is completed in time to start scanning for the s...