Abstract: A system for cleaning lower print head structure of ink jet printing apparatus effects: (i) a condensation cycle wherein a droplet stream(s) are directed past such print head structure in a solvent condensing mode, (ii) a drying cycle in which air is directed across said print head structure to remove condensed solvent and (ii) a heating cycle wherein the lower print head structure is heated to a temperature obviating condensation of solvent from said stream(s).

Abstract: A cleaning system for ink jet printing orifices includes cooperative elements which provide varying pressure differentials across the orifice plate that oscillate ink into and out of the orifices. In one embodiment the pressure differentials are implemented by varying the impedance to ink cross-flow through a print head cavity while pressurizing a region around the exterior of the orifices.

Abstract: A home station of an ink jet printing apparatus is adapted to seal operative print head portions from the ambient atmosphere for storage and includes (i) a housing for collecting ink from the print head, during start-up and testing operations, (ii) a sensor for receiving ink droplets and detecting their charge condition and (iii) a fluid handling configuration that electrically decouples the ink in contact with the sensor from ink being returned from the housing for recirculation.

Abstract: An ink jet printer having an ink supply tank and a constant volume fluid pump which pumps ink through a supply line to a print head and, during a start up sequence, to a pressurizing line having a fluid accumulator which rapidly increases the line pressure of the system until a predetermined ink pressure within the print head is reached. The pressure is sensed by a transducer adjacent the print head, and an outlet valve is actuated to close the flow of ink through the head abruptly, thereby creating a pressure wave which initiates ink flow through the orifices of the print head. In order to minimize contamination of ink in the supply line, the pressurizing line conveys ink back to the supply tank.

Abstract: An ink jet print head includes a manifold defining a fluid receiving reservoir, and an orifice plate mounted on the manifold and defining a plurality of orifices which communicate with the reservoir. Fluid flows through the orifices and emerges as fluid filaments which break up into jet drop streams. A stimulator transducer contacts the orifice plate and, upon receipt of a drive signal, vibrates the orifice plate so as to cause bending waves to travel along the plate. The bending waves stimulate the breakup of the jet drop streams. A sensor transducer is mounted on the orifice plate at the opposite end thereof from the stimulator transducer. The sensor transducer produces an electrical feedback signal which is proportional in amplitude to the amplitude of the bending waves. This feedback signal is used by a drive circuit to control the amplitude of the drive signal applied to the stimulator transducer.