Abstract: An ink jet printer includes a print head having a plurality of piezoelectric driving elements selectively energizable to cause ejection of droplets of ink through nozzles in a nozzle plate. Ink is supplied to the print head from an ink reservoir which is connected to a bellows device. The ink reservoir and the bellows device together form an air-tight container. The bellows device has a resilient form of construction so as to tend to increase the volume of the container. As a result, an appropriate underpressure is maintained in respect of the ink in the nozzles, such underpressure being necessary to prevent ink escaping from the nozzles under quiescent conditions. In operation, the bellows device progressively collapses so as to reduce the rate at which the underpressure increases as ink is ejected, thereby prolonging the period for which the underpressure is maintained within a desired operating range.

Abstract: In ink jet printing, the ink droplets formed at the nozzle of the print head are selectively guided by tilting the nozzle against a resilient portion of the print head and relative to the normal ink droplet propelling direction. The tilting movement is accomplished by an electromagnet or by using conductive wires operably associated with permanent magnet plates in an arrangement such that the pivot of the tilting movement is located at the center of the orifice through the nozzle.

Abstract: The ink in an ink jet printer is accelerated by means of cylindrically-shaped electromagnetically energized pressure waves wherein plates of metal serve as electrodes between which a capacitor is discharged. The capacitor along with the resistance losses and the inductance of the leads represent a damped oscillating circuit to reduce the back pressure waves. Other means of damping include a soft hose having an exponentially shaped portion, porous material in a passageway between a pair of air chambers, and a plastic foil placed between the pressure wave drive means and the nozzle.

Abstract: The ink in a continuous moving stream is caused to be deflected at a point inside the closed ink system by means of timely short pulses to effect the printing operation wherein only deflected ink in the form of ink droplets are ejected through the nozzle. The speed of the ejected droplets depends upon the speed of the continuously-flowing ink and not on the energy of the deflection pulse.

Abstract: Printing of characters in non-impact manner by means of ink droplets which are driven through the nozzle of an inking device is optically sensed and the existence, the position, the size and the condition of each ink spot or mark are determined. The desired printing signals are generated and input in a signal shaping circuit and these signals are compared with the actual signals from the optical sensor and the ink droplet drive means is changed or altered to correct the printing.

Abstract: An ink droplet sensing means for detecting whether or not droplets are impinging on record media during ink jet printing operations. A synthetic foil having a metal layer is placed over a counter electrode having a rough surface on one side and a voltage is then applied to the electrode and the metal layer. Ink droplets impinging on the foil momentarily deflect the foil and cause a change in capacity which in turn causes a voltage change at the electrode. The voltage change is coupled through a capacitor and an amplifier and through recognition logic for evaluation of the signals.