Abstract: A drop-on-demand ink-jet printing head has an ink chamber filled with ink from an ink supply reservoir. The ink chamber has a deflectable upper elastic surface, a deflection of which increases ink fluid pressure. A deflection of said surface exciting a plurality of resonant pressure vibration modes within the chamber. A pressure increase within the chamber causing an ink droplet to be projected out a nozzle at one end of the chamber. A piezoelectric transducer is fixed on the elastic surface to deflect it and excite resonant vibration with a plurality of nodes and loops or antinodes. The transducer is positioned on the elastic surface at one of the loops or antinodes of a preselected one of the pressure vibration modes to excite the pressure modes with a short time constant (high frequency) which enables a very fine droplet of small volume to be projected. This can be done without reducing the cross sectional area of the nozzle or the velocity of the droplet.

Abstract: A multi-nozzle ink drop-on-demand type of ink-jet printing head is able to deliver ink droplets at a higher rate of speed through a use of capillary action. Each of the many nozzles receives the ink required to form a droplet from an individually associated pressure chamber which is squeezed by its own (preferably piezoelectric) driving transducer. A capillary supply path by-passes each of the pressure chambers to provide an initial ink supply which is the start of a droplet formation that is completed upon the operation of the driving transducer. Thus, a time lag is eliminated, which would otherwise be required to start the droplet formation, and that lag elimination enables a faster ink jet response.

Abstract: A print mechanism includes plural print heads arranged in a horizontal direction with each print head including a plurality of nozzles arranged in a vertical direction. The entire print mechanism is disposed on a carriage movable in the horizontal direction. Each of the print heads is preferably supplied with a different color ink, and the printing signals used to energize the nozzles in each print head are delayed for the second and subsequent print heads by an amount corresponding to the time required for the carriage to move horizontally through the displacement between the first print head and the second and subsequent print heads.