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

Adriano Fetta

Alessandro Scardovi

Renato Conta

Mario Buat

Aldo Chiaro

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

One or more printing elements in tube form with a capillary nozzle at one end are mounted in aligned and mutually parallel relationship with a cavity in a support. The printing elements have piezoelectric sleeves thereon and are embedded in a filling of polymerised resin which fills the cavity. They are disposed in such a way that the nozzles project externally from the support while the other ends communicate with a common ink reservoir. The upper wall of the reservoir at each tube is arched with the highest region aligned with the corresponding tube in such a way that any bubbles in the ink can be easily expelled by way of the nozzles. A capillary filter separates the chamber of the reservoir from an ink feed conduit to prevent impurities or air bubbles from passing therethrough. In another embodiment, the reservoir is partitioned into a plurality of separate chambers to ensure that emptying of one tube does not affect operation of the adjacent tubes.

Ink jet printing head

The apparatus is of the type wherein a piezoelectric transducer (19) is selectively operated to produce a pressure wave in the ink in a duct (16, 22), which causes a droplet of ink to be expelled from the nozzle (18). In order to absorb the energy of the pressure wave which is directed towards the ink reservoir (47) the duct comprises a portion (22) of viscoelastic material, which is so dimensioned as to damp the resonance of the duct for frequencies higher than a predetermined cut-off frequency. Frequencies which are lower than the cut-off frequency however are damped by an hour-glass shaped constriction (34) in a tube (33) disposed between the viscoelastic portion (22) of the duct and the reservoir (47). The second portion (22) of the duct comprises a polyamide base material, the modulus of elasticity of which is substantially stable over a wide range of possible operating temperatures. The second portion of the duct may comprise a flexible tube (22) or a double spiral passage (not shown) provided between two substantially square plates.

Growing community of inventors

Castellamonte, Italy

Adriano Fetta