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Printer Carrier Drive Synchronization

IP.com Disclosure Number: IPCOM000081947D
Original Publication Date: 1974-Sep-01
Included in the Prior Art Database: 2005-Feb-28
Document File: 3 page(s) / 60K

Publishing Venue

IBM

Related People

Ross, CO: AUTHOR

Abstract

Where the print wheel in a printer is driven by an AC synchronous motor and the motor driving the print wheel carrier is driven from a constant-frequency source, variations in the line frequency of the source energizing the print wheel motor can cause either more or fewer characters to be presented as the carrier moves across the print line, and the right-hand character position could vary as much as 2-2/3 columns.

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Printer Carrier Drive Synchronization

Where the print wheel in a printer is driven by an AC synchronous motor and the motor driving the print wheel carrier is driven from a constant-frequency source, variations in the line frequency of the source energizing the print wheel motor can cause either more or fewer characters to be presented as the carrier moves across the print line, and the right-hand character position could vary as much as 2-2/3 columns.

This can be prevented by using the arrangement shown in the drawing. As shown, a flip-flop 48 may be turned on coincidentally with a particular index pulse from a type wheel emitter, not shown, through a counter 21 and AND 44 which provides a Start signal, to provide a ramp of increasing frequency pulses to accelerate the stepper motor and carrier. Flip-flop 48 turns on carrier start sequence flip-flop 1 which gates a series of ANDs 2 through 2x, which produce the acceleration ramp pulses by appropriately decoding type counter 21. At the end of the last acceleration advance pulse (from AND 2x) inverter 3 resets flip- flop 1, and at this time the carrier is up to speed.

ANDs 2 through 2x are now degated and through inverter 4, ANDs 5 through 5y are gated on. The number of index pulses between each decode 2x through 5y is the same, as will be explained hereinafter. These pulses cause the carrier to advance at a speed which is automatically synchronized with the print wheel rotational speed.

When flip-flop 48 is turned off by AND 54, inverter 6 turns on a carrier stop sequence flip-flop 7 which enables deceleration decode ANDs 8 through 8z. These ANDs, if required, produce a ramp of decreasing frequency pulses which cause the desired stopping sequence for the carrier stepper motor. At the end of the last decelerate advance pulse (from AND 8z) inverter 9 resets flip-flop 7: at this time the carrier is stopped and a complete cycle of operations (accelerate, run and stop) synchronous with the print wheel has been completed. (OR 10 simply combines all the decoded pulses to a single "phase advance pulse", which drives common to the art motor phase advance triggers and driver circuitry....