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:
May. 12, 1992
Filed:
Mar. 11, 1991
C S Chan, Boise, ID (US);
Alfred I Pan, Sunnyvale, CA (US);
Hewlett-Packard Company, Palo Alto, CA (US);
Abstract
A system for delivering ink to print heads in thermal ink jet printers includes a liquid compartment with a gas space thereabove at sub-atmospheric pressure, a hydrophobic membrane mounted between the liquid compartment and the surrounding environment for allowing ambient gases to bubble into the liquid while preventing liquid from flowing in the opposite direction through the membrane, at least one chamber that provides a reservoir of ink with a gas space thereabove at sub-atmospheric pressure, and a manifold connecting the gas space in the liquid compartment with the gas space in the ink chamber. Thermal ink jet print heads are mounted in ink-flow communication with the ink chamber and are adapted for ejecting ink onto sheets to be printed. In operation, ink flows into the thermal ink jet print heads at a flow rate which is regulated by a generally constant back pressure. This novel pen body construction enables the hydrophobic membrane to be completely isolated from the ink in the multiple ink reservoirs of the pen, with the advantage that ingredients and additives within the ink do not degrade the surface properties of the hydrophobic membrane material.