The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Dec. 01, 1992
Filed:
May. 01, 1991
King-Wah W Yeung, Cupertino, CA (US);
Hewlett-Packard Company, Palo Alto, CA (US);
Abstract
This document discloses a method and apparatus for real-time control of the temperature of thermal ink jet printheads and thermal printheads through the use of nonprinting pulses. A closed-loop system produces nonprinting pulses in response to a difference between a reference temperature signal and a printhead temperature signal produced by a temperature sensor on the printhead so that the printhead operates at a constant elevated temperature. The reference temperature signal can specify an operating temperature anywhere between 10.degree. C. and 100.degree. C. above room temperature. The closed-loop system can have multiple loops with different response times so that complex nonlinear responses to changes in the printhead temperature can be obtained. The open-loop system transmits nonprinting pulses to the printhead for each printing interval that the printer does not eject a drop. Also, this document discloses a method for measuring the energy transfer characteristics of a printhead. This method is used to determine how much energy open-loop nonprinting pulses should transmit within one printing interval to the printhead to prevent fluctuations in the temperature of the printhead caused by variations in the printer output.