Thomas K Fields

US Patent:

6565176, May 20, 2003

Filed:

May 25, 2001

Appl. No.:

09/865881

Inventors:

Frank Edward Anderson - Sadieville KY
Thomas Austin Fields - Winchester KY
Paul William Graf - Lexington KY
Yimin Guan - Lexington KY
George Keith Parish - Winchester KY
Kent Lee Ubellacker - Georgetown KY

Assignee:

Lexmark International, Inc. - Lexington KY

International Classification:

B41J 2938

US Classification:

347 14, 347 11

Abstract:

A thermal ink jet printing apparatus maintains stable printing output as certain characteristics of the apparatus change over its operational lifetime. The apparatus includes an ink jet print head with resistive heating elements for receiving electrical energy pulses having a voltage level and for transferring heat energy pulses having a desired energy level into adjacent ink based on the electrical energy pulses. The print head includes nozzles associated with the resistive heating elements through which droplets of the ink are ejected when the heat energy pulses are transferred into the ink. The apparatus further includes a printer controller in electrical communication with the print head. The printer controller determines a pulse count indicative of a number of electrical energy pulses, applies the electrical energy pulses having a first pulse width to the resistive heating elements when the pulse count is less than a threshold value, and applies the electrical energy pulses having an adjusted pulse width to the resistive heating elements when the pulse count exceeds the threshold value. The difference in the first and the adjusted pulse widths compensates for changes in the electrical resistance of the resistive heating elements over time.

US Patent:

7205738, Apr 17, 2007

Filed:

Mar 24, 2004

Appl. No.:

10/808101

Inventors:

Danny Keith Chapman - Georgetown KY, US
Thomas Austin Fields - Winchester KY, US
Steven Michael Turney - Lexington KY, US

Assignee:

Lexmark International, Inc. - Lexington KY

International Classification:

H01R 39/46
H02K 13/00
H02P 25/12

US Classification:

318439, 318254, 318138, 318461, 318432, 318434

Abstract:

A motor control circuit uses a stored commutation table to effect time-based commutation of a brushless dc motor. Each entry in the commutation table defines a motor winding commutation state, and an exemplary method of open-loop motor control based on the commutation table comprises commutating the motor based on sequentially selecting table entries at a desired selection rate. That is, motor speed is controlled precisely by controlling the sequential selection rate rather than by relying on feedback from the motor. However, motor feedback for closed-loop control may be used in some modes of operation. For example, the method may include closed-loop control or open-loop control depending on the motor speed range, and may transition from closed-loop to open-loop control.