Some printheads require some servicing routines during the normal operation in order to keep the printheads in good conditions. Typically, the servicing routines consist of a combination of spitting, where the resistors are activated to spit ink, and blow primes, that consist of applying air pressure on the printhead vent to open the printhead regulator and eject some ink. Typically, the result of performing a non‐effective prime is a defect on the Image Quality, since during the servicing routines, the amount of ink ejected during a prime is lower than the required. This situation could occur if there is an obstruction on the air channel that connects the air pump to the printhead regulator. Note that even though some primer subsystem includes a pressure sensor, since the volume of the air channel is too small, it may be difficult to detect an obstruction based on the pressurization profile compared to a regular prime. This invention describes an automatic process to detect a non‐effective prime based on monitoring the temperature measured by the TSR (Temperature Sensor Resistance) located in the printhead. Depending on the temperature profile during a blow‐prime, a non‐effective prime can be detected. Furthermore, the solution allows to detect drooling situations.
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INC, HP, "AUTOMATIC DETECTION OF A NON-EFFECTIVE PRIME", Technical Disclosure Commons, (August 24, 2022)