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Servoing System for Hammer for Dot Drum Helix

IP.com Disclosure Number: IPCOM000059886D
Original Publication Date: 1986-Feb-01
Included in the Prior Art Database: 2005-Mar-08
Document File: 2 page(s) / 35K

Publishing Venue

IBM

Related People

Lane, R: AUTHOR

Abstract

A technique is described for adjustment of firing time to compensate for drum speed variation and flight-time variations. As a high speed printer, the dot drum helix must have accurate controlled firing of the print hammer relative to the dot on the drum. For example, at a drum speed of 100 inches/second, a firing error of 10 microseconds causes a misplaced print dot on the paper of 0.001 inch.

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Servoing System for Hammer for Dot Drum Helix

A technique is described for adjustment of firing time to compensate for drum speed variation and flight-time variations. As a high speed printer, the dot drum helix must have accurate controlled firing of the print hammer relative to the dot on the drum. For example, at a drum speed of 100 inches/second, a firing error of 10 microseconds causes a misplaced print dot on the paper of 0.001 inch.

Most hammer actuators have a flight-time error of more than Å35 microseconds, which would cause a total displacement of 0.007 inch in the position of the printed dot at the above-noted speed. It would be desirable to adjust the firing time in accordance with changes in drum speed and to compensate for flight-time variations of the hammers. A servoing system is described herein which uses the print dots on the drum as sense elements to determine the relative position of the drum with the hammers just prior to the firing of the hammers.

There is a fixed relationship of any one dot to all other dots in the helix. Therefore, every dot has a repeatable reference to any dot that is about to be struck by the print hammer. Fig. 1 shows a cross section of the drum with 4 print dots, a hammer, and three sensors. Sensors B, C and D, can be positioned so that the dots are sensed prior to the arrival of dot A at the print position. The sensed signals from sensors B, C and D, trigger a delay pulse that fires the hammer when dot A is in the correct position. Fig. 2 shows the circumference of the drum in a flat layout with a 12-dot helix, and three sensors B, C and D, each ...