Method of operating an ink jet to reduce print quality degradation resulting from rectified diffusion

In an ink jet print head of a type including an ink pressure chamber having an inlet coupled to a source of hot melt ink and an outlet coupled to an orifice, and a driver for controlling the volume of the ink pressure chamber in response to an electrical signal in order to eject an ink drop from the orifice, the ink pressure chamber further having air bubbles in the air saturated ink therein which experience a growth when pressure applied to the ink within the ink pressure chamber repeatedly is subambient pressure and in negative pressure terms is greater than or equal to a threshold pressure amount of greater than about minus 10 psig at a repetition rate of about 8 Khz or greater, a method comprising applying a bipolar electrical signal to the driver in a manner to generate within said ink pressure chamber sub-ambient pressure waves of a character that in negative pressure terms is less than the threshold pressure amount and thereby inhibits growth of air bubbles therein.

In a printer system including a print head of a type having an ink pressure chamber adapted to eject a liquid ink droplet on demand from an orifice to a print media upon altering the volume of said chamber in response to an electrical drive signal, a source of ink that is solid at an ambient operating temperature, and means melting said solid ink for supplying liquid ink to said head chamber, the liquid air saturated ink within the head chamber further having air bubbles therein which experience a growth when pressure applied to the ink within the head chamber is repeatedly less than ambient and is greater than or equal to a threshold pressure amount in negative pressure terms of greater than about minus 10 psig at a repetition rate of about 8 Khz or greater, a method of operating said printer system, comprising the steps of:

• allowing the liquid ink within the head chamber to become substantially saturated with air, and
• causing the electrical drive signal to have an amplitude function including first and second pulses with a wait period of separation between the pulses, said amplitude function being adapted to generate within said head chamber ink pressure waves that apply a pressure to the liquid ink within the head chamber in negative pressure terms that is less than the threshold pressure amount and are characterized by inhibiting growth of air bubbles therein.