1. Technical Field
The present invention relates generally to ink replenishment systems, and more specifically to an ink replenishment system and method for a continuous flow ink jet printer using pressure feedback.
2. Background Art
Since its mass-market introduction in the mid-1970's, ink jet printing continues to be one of the most popular printing technologies. Ink jet is a non-impact dot-matrix printing technology in which droplets of ink are jetted from a small aperture directly to a specified position on a media to create an image. Continuous flow ink jet printing involves a process in which a stream of ink is broken into droplets of uniform size and spacing and passed through an electrical charge. The charged drops are deflected into a gutter for recirculation, and the uncharged drops fly directly onto the media to form an image.
One of the difficulties of continuous flow ink jet ink printing involves ink quality degradation caused during the recirculation process. In particular, as the ink flows from the print nozzles, water from the ink evaporates. Accordingly, the ink that is recirculated back to the ink tank tends to be more viscous. To compensate, a replenishment tank holding replenishment fluid is connected with a valve to the ink tank to help maintain a constant ink viscosity.
In current embodiments, the amount of replenishment fluid that flows to the ink tank is controlled using some type of manual adjustment. In one typical embodiment, the valve connecting the replenishment tank to the ink tank allows a fixed amount of replenishment fluid to enter the ink tank during periodic activations of the valve. Unfortunately, fluctuations in external conditions, such as humidity, can significantly impact the amount of required replenishment fluid. Accordingly, incorrect viscosity can occur over relatively short durations and result in print failure.
Thus, a need exists for an ink replenishment system that can ensure a correct amount of replenishment fluid is being added to the ink tank in a continuous flow ink jet printer.