Ing C. Olivetti C., S.p.a.

Mario Buat

Gian D Dagna

Renato Conta

Alessandro Scardovi

Franco Knirsch

Riccardo Brescia

Giandomenico Dagna

Aquilino Barbero

Giovanni Gianolini

Adriano Fetta

In a thermal ink jet print head the ink is expelled in the form of small drops through a plurality of nozzles communicating with corresponding expulsion chambers for expulsion of the ink through the effect of rapid heating of heater elements contained in the expulsion chambers. The nozzles, the expulsion chambers, the heater elements and the associated electrical conductors are constructed in a plurality of metal layers and insulating layers supported by a silicon plate. The plate is fixed to the structure of the head and is supplied with ink contained in a movable cartridge fitted to the structure of the head. The cartridge comprises a rigid reservoir containing a sponge saturated with ink which can be hydraulically connected to the head by means of a needle-type conduit mounted on the head and which perforates a rubber membrane of the cartridge. During the periods of storage and inactivity of the head, the cartridge is removed, permitting drying of the nozzles to avoid possible nozzle blockages and corrosion of the layers of the plate by the ink.

Thermal ink jet print head with removable ink cartridge

The device comprises a plurality of ink reservoirs, each connected to a number of nozzles (22) equidistant along a corresponding row. The nozzles connected to the various reservoirs are spaced apart vertically by at least one line space. The device can be used for printing different lines in parallel, moreover subdividing the length of the line, or for printing different zones of the sheet in facsimile. The ink is kept in circulation between the reservoirs and the nozzles by a common peristaltic pump which acts by a series of actuating elements on the discharge ducts for the inks in the reservoirs. The reservoirs may contain inks of different colors to permit printing in different colors or polychrome facsimile printing by additive or subtractive synthesis of the colors. The ink is conductive and is kept at earth potential, while electrodes (23) disposed outside the corresponding nozzles (22) are energized selectively to produce sprays of particles of ink from the nozzles. The ink contains a mixture of a dye of direct or solvent or acid type with a solution of water, electrolytic compounds, moistening agents, thickeners, preserving agents and antifoaming agent. The ink is prepared by mixing the compounds under agitation, then mixing in the dye until a predetermined acidity is obtained and finally filtering it and sealing it in the pack in the absence of air.

Ink-jet printing device

The head is provided for a conducting ink and comprises a closed container (14) carrying two electrodes and a nozzle (18). The head is removably mounted on a carriage (13) and is replaced when the ink is exhausted. The container (14) is divided into two cavities (71 and 72) which are in communication by way of an aperture (73, 74, 75) in order to cause ink to flow to the nozzle and to remove bubbles. To ensure that the bubbles do not cause an increase in the pressure in the container, causing the ink to discharge from the nozzle, the container comprises an expansible cavity formed by a bag-type diaphragm (83) and a compression spring (82) which tends to cause expansion of the cavity. The container is filled with ink, while holding the spring in a compressed condition. As the ink decreases, the spring expands, maintaining a slight depression within the container.

Serial ink jet printing head

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.

Selective ink-jet printing device

The device comprises an electrically insulating ink container containing one electrode and a counter-electrode disposed adjacent to the jet nozzle which is laser-bored through the container cover plate. The two electrodes are excited by a voltage pulse such as to generate a spark between the ink meniscus and the counter-electrode, and to expel a plurality of ink particles, rather than a single blob. The ink can be kept in circulation between the container and a reservoir 51 by means of a pump. The meniscus can be kept outside the nozzle by means of a second nozzle coaxial to the first, or by a suitable arrangement of the ink hydraulic circuit. In the case of magnetic ink, the meniscus is pulled back by a magnetic field. The ink can also be brought in front of the nozzle by capillarity.

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Carema, Italy

Mario Buat