The problems associated with the premature drying of liquids such as inks, within fluid delivery devices such as inkjet printers, are known. The premature drying of liquids causes the plugging of ejection nozzles that will either impede or totally prevent liquids from being delivered through the nozzle and onto a desired delivery medium. The plugging that occurs within liquid ejection nozzles has created a need for methods that remove such blockages, such as purging of the nozzles.
Those skilled in the art of inkjet printers are aware that software exists to verify the proper operation of liquid ejection nozzles. The software also provides various routines to exercise those nozzles to purge them of dried or drying liquids. A significant drawback to purging of nozzles within fluid ejection systems exists in that the purged fluids must be deposited somewhere. This is typically accomplished by depositing the purged fluids into a sponge. However, purging receptacles such as sponges and the like have limited storage volume and become full requiring costly and often inconvenient service requirements. Service, the replacement of sponges, and the use of cleaning cycles increases the cost of printing and adds to the complexity of printer mechanisms. Additionally, full and saturated receptacles can contaminate the very nozzles that you are trying to clean, by virtue of cross-contaminating wet sponge material into nozzles that are already clean.
Also, in typical printing applications, the image-wise requirement of placing ink droplets upon a receiver will leave certain nozzles unused. This exacerbates the drying of ink within the unused nozzles, because of the rapid reciprocation of the print head. The additional motion enhances the movement of air over the nozzles, and thus directly increases the rate of the evaporation of the fluids waiting to be ejected. Additionally, inks, including dye and pigment based inks, exhibit unique physical drying properties based upon their individual formulations, with the rate of those drying properties being accelerated when the ink is idle and exposed to the atmosphere at the meniscus of an ejector nozzle.
U.S. Pat. No. 6,695,441 B2, issued to Asano on Feb. 24, 2004, discloses a stirring device that utilizes an ultrasonic transducer that applies ultrasonic vibrations to ink in order to overcome problems such as molecular over-concentration due to molecular coupling, the sedimentation of suspended particles and the cohesion of particles within an ink. Asano teaches that the molecular-weight distribution of inks increases because of molecular clumping and causes erratic or clogged ink nozzles, and additionally that the practice of simple ink stirring does not sufficiently address problems such as sedimentation or cohesion, those types of problem being solved by the aggressive method of using a complicated and costly ultrasonic device.
U.S. Pat. No. 6,172,693 B1, issued to Minemoto et al. on Jan. 9, 2001, also discloses a method of stirring a fluid. This method discusses a plurality of electrophoretic electrodes that react with the polarity of particles that are suspended within a fluid. These particles in turn correspond with and react to a plurality of ejecting electrodes whose functions are also based upon the polarity of the suspended particles. Stirring electrodes that are disposed in proximity to the ejecting electrodes serve to stir the polarity-based color particles that are suspended within the fluid carrier that delivers those particles to the ejecting electrodes. This charge-based stirring of the suspended particles promotes proper dispersion of the particles in the area of an ejection port, thus preventing those particles from plugging the ejection port and blocking their ejection, the ejection of a particle being accomplished by virtue of electrophoresis.