Abstract: A high performance ink jet is operated in a fill-before-fire mode. The ink jet is characterized by at least one resonant frequency in excess of 10 kHz creating an upper limit for a frequency of stable operation. During operation, the ink jet is characterized by ejecting droplets of substantially equal velocity and/or size for various frequencies in an operating range extending from 0 to a fequency equal to or in excess of 5 kHz.

Abstract: A high density printer includes a printing plate having an array of through holes of capillary dimension, and individual heaters located within each hole near one face of the printing plate, whereby printing is accomplished by placing the other face of the printing plate in contact with a pool of liquified phase change ink for a period of time sufficient to allow ink to fill each hole via capillary action, after which time the printing plate is removed from the ink and allowed to cool for solidifying the ink within each hole, whereafter selective ones of the heaters are energized for melting ink in associated holes, whereupon the ink expands away from the solidified ink in the portions of the holes below the heaters, causing ink to protrude from the associated holes on the one face in a desired pattern for transfer to a substrate brought into intimate contact with the one face.

Abstract: A novel hot melt impulse ink jet ink is disclosed which comprises a C.sub.20 -C.sub.24 acid or alcohol containing vehicle, preferably behenic acid, and a suitable coloring agent. The preferred ink has a melting point above about 65.degree. C., exhibits very good jettability, good heat stability at a reservoir temperature of 90.degree. C., good material compatability, and an improved print quality. The preferred ink comprises about 80% natural behenic acid, 15% of a ketone (such as stearone), 3% coloring agent, and 2% of a plasticizer intended to improve print quality. The subject inks are jetted at relatively high temperatures (80.degree.-90.degree. C.) using impulse ink jet devices. Upon impact with the target substrate the subject inks freeze to produce a high quality print having a smear resistance approximately equal to IBM copy, and cracking resistance better than such copy.

Abstract: Ink jet apparatus utilizing hot melt ink and method of operation of that apparatus, the apparatus having a pressure source for repriming the system following non-use and freezing of the ink in the reservoir. The repriming operation may be carried out either manually or automatically, as long as permitted by the sensed level of the ink in the reservoir system.

Abstract: An ink jet includes a variable volume chamber with an ink droplet ejecting orifice. The volume of the chamber is varied by a transducer which expands and contracts in a direction having at least a component extending parallel with the axis ink droplet ejection from the orifice. The transducer communicates with a moveable wall of the chamber which has a sufficiently small are a such that the difference in the pressure pulse transit times from each point on the wall to the ink droplet ejection orifice is less than 1 microsecond.

Abstract: Ink jet apparatus utilizing hot melt ink, having a reservoir system which contains the ink and maintains it in its melted phase when the apparatus is in use, and a tilt valve positioned above the reservoir, the valve having respective normally opened and closed positions, and providing both an air vent to the reservoir and a fill port for draining melted ink into the reservoir when in its normally opened position. Tilt valve may be placed into its closed position either by tilting the reservoir beyond a predetermined angle, or by automatic tilting of the valve actuator when the ink jet priming system is activated.

Abstract: A series of solid state ink members extends in an elongated array above a heated ink reservoir for a phase change ink jet apparatus. The members then advance along a path extending through the elongated array to a discharge location at one end of the path whereupon the members are dropped into the reservoir for melting. By threadedly engaging the members in pellet form with a rotatable drive, or threadedly engaging a drive member by the threaded drive shaft, the members may be suitably pushed along the path. In the alternative, the hot melt ink may take a granular form and be advanced by a rotatable, auger-like surface.

Abstract: A demand ink jet employs removable cartridges of hot melt ink. When the temperature of the ink within the cartridge is raised, the ink melts and drains from the cartridge into the supply system. Each of the cartridges may include ink of a different color so as to permit multi-color printing.

Abstract: Hot melt ink is maintained in a solid state at a fixed location along with a smaller quantity of liquid ink in a buffer reservoir at the same location. When ink is called for in the reservoir of a scanning imaging head, the head is moved to a position coupled to the buffer reservoir whereupon the previously melted ink from the solid state supply may be coupled into the reservoir of the imaging head.

Abstract: Two ink jet modules are employed, having an ink supply system with a bubble trap chamber having level sensors. By maintaining the proper orientation of one of the modules with respect to the vertical, the other module may be placed in any orientation so as to eject droplets in any orientation from that module.