Patent ID: 6644774
Filing Date: 2003-11-11
Classification: B41J

Abstract:
A thermal ink jet printhead and print control system for an ink jet printer having means to detect an out-of-ink condition during a printing operation by monitoring the printhead temperature, comprising:a structure having an ink supplying reservoir with an ink inlet thereto for receiving ink from an ink supply, a plurality of droplet ejecting nozzles, and a plurality of capillarily filled ink flow directing channels that interconnect the reservoir to each of the nozzles; a plurality of selectively addressable heating elements, one heating element being located in each channel, the heating elements producing momentary ink vapor bubbles when energized to eject ink droplets; a temperature sensor for sensing the temperature of said structure; a control circuit for selectively applying electrical signals to the heating elements for energization thereof in response to image data signals received thereby, the control circuit including a memory for the storage of a predetermined temperature indicative of the maximum allowable operating temperature of the structure, means for comparing the sensed temperature of said structure by said sensor with said predetermined temperature stored in said memory and generating an overheating signal whenever said sensed temperature is greater than the predetermined temperature stored in said memory; said control circuit, in response to a first overheating signal generated by said means for comparing and generating and after the beginning of a printing operation, being programmed to assume the printhead has become deprimed and causes said printhead to be primed before the printing operation can be continued; and said control circuit, in response to a second overheating signal generated by said means for comparing and generating and immediately after the printhead has been primed in response to a first overheating signal, being programmed to assume a depleted ink supply and a continued printing operation is prevented until said depleted ink supply is replaced.