Abstract: A droplet of ink 11 is expelled from a nozzle in a wall, so as to strike a printing medium, by suddenly moving the wall towards the ink 11 with which it is in contact. This movement is effected by energizing a piezoelectric sleeve. The ink droplet is expelled by virtue of the inertia of the ink resisting the movement of the wall and creating pressure. Practical embodiments are described in which the wall containing the nozzle is formed by the tapered end of a capillary tube.

Abstract: An ink-jet printer includes a reservoir filled with ink and an ink duct communicating with the reservoir. The duct has a terminal portion with a capillary nozzle for projecting the ink, and an intermediate portion between the reservoir and the terminal portion. Transducer means are associated with the terminal portion of the duct for generating a first pressure wave in the ink, which is directed towards the nozzle and causes a droplet of ink to be discharged through the nozzle. Energy absorption means cooperate with the ink in the intermediate portion of the duct and comprise an elongate container adjacent at least part of the intermediate portion of the duct and having at least one wall which is in contact with the ink and can deform resiliently under the action of a second pressure wave associated with the first pressure wave and directed towards the intermediate portion of the duct.

Abstract: The device comprises a printing head (15) constituted by an insulating container (19) with a capillary nozzle (36). The electrically conductive ink is kept under circulation in the container via a feed tube (26, 23) and a return tube (27, 24) leading to a suction pump, in order to allow the formation of a convex meniscus at the exit aperture of the nozzle (36) and eliminate any vapor bubbles. A pulse generator creates a voltage of a predetermined value and duration between an electrode (37) external to the nozzle and an electrode (23) in contact with the ink, in order to create a state of excitation of the meniscus and partial vaporization of a layer of ink, such as to expel a plurality of ink particles. The head is mounted on a carriage movable transversely to the paper, which advances at each stroke reversal of the head.

Abstract: The tracing element is carried by one vertex of an articulated parallelogram, of which the arms are constituted by thin steel or glass fibres associated with a plastics coating or matrix for damping vibrations. The arms are moved by servocontrols constituted by electromagnets with moving coils having a length less than the length of the corresponding magnet pole piece. The coils are formed from a conductor of square or rectangular cross-section in order to provide maximum packing for the turns.

Abstract: The printer comprises a ROM recorded for each character with a set of pairs of numerical instructions, of which one represents the direction of a constant velocity vector of the tracing element for tracing a segment of the character, and the other represents the duration for which that velocity has to be applied to said element. The direction instruction is decoded by a decoder in order to generate two orthogonal components which control two servo-mechanism by way of two corresponding D/A converters. The duration of the movement is controlled by a counter loaded by the duration instruction and decremented by a clock signal. Every time the counter is emptied a logic unit responds by addressing the next byte in the ROM.

Abstract: A correctable print is obtained by using an easily sublimable ink. Said print is completely erased when heated at a temperature insufficient to cause the darkening of the paper, by means of a hot point, of hot air, or of radiant energy.

Abstract: The printer is provided with a single tracing element for tracing characters under the control of stored digital instructions corresponding to a set of segments of the character. The tracing element is moved on the printing surface according to a pair of coordinates, within the limits of each character. To this end it is carried by a frame including a pair of hinged elements directed according to the two coordinates and moved by a pair of electromagnets. These latter are controlled by feed back circuits including a pair of position sensors. The frame is mounted on a carriage transversely movable according to other instruction for letter spacing. A movement of the printing element according to a third coordinate causes the tracing element to press the paper with a pressure corresponding to the thickness of the sign.

Abstract: A removably mountable electrothermal print head for writing dots-matrix characters while moving along a thermosensitive recording medium and a mounting for the hand or a movable carriage of a printer, the head comprises a plurality of electrically energizable resistive printing elements coated on a support; the outer surface of said elements is partly cylindrical with the generatrices in parallel relation with a common direction which is transversal with respect to the printing line of the recording medium. The print head is positioned with respect to the recording medium with the part-cylindrical outer surface of the resistive printing elements in tangential relation with the recording medium. The printing head is positioned on and removably fixed to the carriage by a manually actuatable latch.

Abstract: A removably mountable electrothermal print head for writing dots-matrix characters while moving along a thermosensitive recording medium and a mounting for the hand or a movable carriage of a printer, the head comprises a plurality of electrically energizable resistive printing elements coated on a support; the outer surface of said elements is partly cylindrical with the generatrices in parallel relation with a common direction which is transversal with respect to the printing line of the recording medium. The print head is positioned with respect to the recording medium with the part-cylindrical outer surface of the resistive printing elements in tangential relation with the recording medium. The printing head is positioned on and removably fixed to the carriage by a manually actuatable latch.

Abstract: A removably mountable electrothermal print head for writing dots-matrix characters while moving along a thermosensitive recording medium and a mounting for the hand or a movable carriage of a printer, the head comprises a plurality of electrically energizable resistive printing elements coated on a support; the outer surface of said elements is partly cylindrical with the generatrices in parallel relation with a common direction which is transversal with respect to the printing line of the recording medium. The print head is positioned with respect to the recording medium with the part-cylindrical outer surface of the resistive printing elements in tangential relation with the recording medium. The printing head is positioned on and removably fixed to the carriage by a manually actuatable latch.