Ink delivery pressure control

Abstract

For control of static ink delivery pressure, a system and method make use of an outer chamber having a first outlet for delivery of ink to an ink printing mechanism, an inner chamber having a second outlet for delivery of ink to the outer chamber, and a pressure source that applies negative pressure to the outer chamber. The inner chamber maintains an internal negative pressure that is selected to control a level of the ink within the outer chamber relative to a height of the second outlet within the outer chamber. In particular, inner chamber maintains the ink level at a substantially constant level by replenishing the volume of ink within the outer chamber upon consumption. When ink is consumed by the ink printing mechanism, the inner chamber delivers a proportional volume of ink to the outer chamber that is sufficient to restore the ink to the desired level. The negative pressure applied to the outer chamber is operative on the substantially constant volume of ink maintained within the outer chamber, and can be readily selected to provide a substantially uniform static ink delivery pressure from the outer chamber to the ink printing mechanism. For an inkjet printhead, the level of negative pressure applied to the outer chamber serves to control static nozzle pressure to avoid excessive wetting that can adversely affect jetting characteristics. The level of negative pressure can be selected based on the physical characteristics of the ink, the printing mechanism, or both.