David Michael Waller

US Patent:

6428156, Aug 6, 2002

Filed:

Nov 2, 1999

Appl. No.:

09/432453

Inventors:

David J. Waller - Fort Collins CO
Melissa D. Boyd - Corvallis OR

Assignee:

Hewlett-Packard Company - Palo Alto CA

International Classification:

B41J 218

US Classification:

347 89

Abstract:

An actively-controlled recirculating ink delivery system is provided that incorporates active control of pressures downstream of the printhead. This is achieved through the use of a device (such as a pump, return valve, combination thereof or similar devices) that provides active control of downstream ink pressures. A pressurized ink supply, pressure sensors, an air and heat exchanger are also provided, thereby improving start up, normal operation, purging and shut down procedures. Because the pressurized ink supply is not restricted to sit at a particular vertical distance below the printhead, backpressure may be changed quickly and easily through electronic control, and system priming is considerably quicker than with conventional air-pressurized systems.