Ink jet printer, particularly for high speed printing

Claim 2

Ink jet printer including a reservoir for an electrically conductive ink, at least one capillary nozzle for ejecting the ink communicating with the reservoir, a first electrode in contact with the conductive ink, a second electrode located at the outlet end of the nozzle and an electrical energisation circuit for applying a voltage pulse between the electrodes for causing the ejection of ink droplets through the nozzle, characterised in that it includes a gas evacuation chamber (43) and in that above the free surface of the ink in the reservoir (13)there is at least one aperture (44) communicating with the evacuation chamber (43).

Claim 3

Printer according to Claim 1, characterised in that the evacuation chamber (43) has associated pump means (48 to 50) for generating a low pressure within the said chamber (43).

Claim 4

Printer according to Claim 2, characterised in that the pump means include a Venturi diffuser (48), a generator (49, 50) for generating a gas flow through the Venturi diffuser (48) and a duct (47) connecting the throat section (48a) of the diffuser (48) with the gas evacuation chamber (43).

Claim 5

Printer according to Claim 2, characterised in that the gas flow generator (49, 50) has adjustment means for varying the intensity of the gas flow in order to control the magnitude of the low pressure produced within the evacuation chamber (43).

Claim 6

Ink jet printer according to any one of the preceding claims, characterised in that the electrical energisation circuit (12)includes adjustment means (33, 33a) which can cause a controlled variation in the energy of the voltage pulses in order to graduate selectively the intensity of the ink sprays ejected by the printer.

Claim 7

Ink jet printer according to any one of the preceding claims, including a plurality of nozzles, characterised in that it includes a plate member (17; 117) defining a wall portion of the reservoir (13) with a laminar substrate (18; 118) of rigid insulating material and metal coatings (20, 21; 120, 121) on the opposite faces of the substrate (18; 118) defining the said first (21; 121) and second (20; 120) electrodes for the plurality of nozzles and a further coating of vitreous material (25; 125) on the surface facing outwardly of the printer (11).

Claim 8

Printer according to Claim 6, characterised in that the nozzles (19) are provided in the form of holes, each of which passes through the substrate (18), one of the metal coatings (20) provided on the face of the substrate (18) facing outwardly of the printer (11) and the said further coating (25) of vitreous material.

Claim 9

Printer according to Claim 6 or Claim 7, characterised in that the substrate (18; 118) is constituted essentially by sintered alumina and has a thickness of substantially 0.2 mm in the region in which the nozzles (19; 119) are provided.

Claim 10

Printer according to any on E of Claims 6 to 8, characterised in that the nozzles(19;119) are made by piercing of the plate element (17; 117) with laser radiation.

Claim 11

Printer according to any one of Claims 6 to 9, characterised in that it includes eight capillary nozzles (19) arranged in an array comprising two parallel rows (columns)each of four nozzles spaced apart at equal distances; the nozzles (19) of the two rows being relatively staggered by a distance equal to half the said inter-nozzle spacing.

Claim 12

Printer according to Claim 10, characterised in that the rows are located at a distance of substantially 1.27 mm apart while the distance between the nozzles (19) in each row is substantially 0.4 mm.

Claim 13

Printer according to any one of Claims 6 to 11, characterised in that the reservoir (13) is provided internally with separator partitions (15) for damping the inertial movements of the ink generated as a result of the movement of the printer (11) during printing.

Claim 14

Printer according to any one of the preceding claims 1 to 9, for printing in several colours, characterised in that the reservoir (13) includes a plurality of separate compartments liquid-tightly sealed from each other, each of which is filled with a different coloured ink, in that a single gas evacuation chamber (43) is provided,and in that above the free surface of the ink in each compartment there is an aperture (44) communicating with the evacuation chamber (43).

Claim 15

Printer according to Claim 13, including a reservoir for an electrically conductive ink, a plurality of capillary nozzles for ejecting the ink communicating with the reservoir, first electrodes in contact with the conductive ink, a plurality of second electrodes each of which )is located in correspondence with the outlet end of one of the nozzles and an electrical energisation circuit for applying between the said first electrode and each of the said second electrodes voltage pulses which cause )the ejection of ink droplets by each nozzle, characterised in that: - the reservoir (13) includes a plurality of separate compartments (115) liquid-tightly sealed from each other, each of which is filled with a different )coloured ink, - the nozzles (119) are aligned in the direction of printing of the printer (10) and each communicates exclusively with one of the compartments, - the electrical energisation circuit (12) includes separate energisation stages for each nozzle (119) in order to achieve the emission of ink sprays of different colours in correspondence with a single printing region, so as to achieve printing in this region with a colour resulting from the chromatic synthesis of the colours of the inks ejected by the nozzles (119).

Claim 16

Printer according to Claim 13 or Claim 14, chatacterised in that four compartments are provided in the reservoir (13), three of which receive inks of colours corresponding to the basic colours of a chromatic triangle, while the other compartment is filled with an ink for black and white printing.

Claim 17

Printer according to any one of the preceding claims, characterised in that means are provided for mounting the printer (11) itself in a printing machine in a position facing a printing surface (S),the mounting means including: - a pair of parallel guides (3, 5) extending transverse the printing surface (S); one (3) of these guides being displaceable with a contained movement approaching the surface (S) itself, - a support carriage (6) for the printer (11) which is slidable longitudinally on the guides (3, 5) and can follow the movable guide (3) in the said movement approaching the printing surface (S), - resilient means (4) for biassing the movable guide (3) towards the printing surface (S), and - a stop or shoe member (26; 126) rigid with the printer (11) which can cooperate slidingly with the printing surface (S) during the movement of the support carriage (6) along the said guides (3, 5) in order to keep the nozzles (19; 119) of the printer (11) at a predetermined distance from the printing surface (S).

Claim 18

Printer according to Claim 16, characterised in that the movable guide (3) is associated with a forked support structure (1), of which the movable guide (3) constitutes a transverse member, provided with two lateral pivoted arms (2), each of which is hinged to the structure of the printing machine at its end (2a) opposite the movable guide (3).

Claim 19

Printer according to Claim 16 and any one of claims 6 to 7, characterised in that the stop or shoe member is constituted essentially by a projection (26; 126) of the said coating of vitreous material (25; 125) applied to the face of the plate member (17; 117) facing outwardly of the device (11).

Claim 20

Printer according to Claim 18, characterised in that the projection has a thickness of about 0.1 mm.

Claim 21

Printer according to Claim 18 or Claim 19, characterised in that the projection is constituted by a vitreous material applied to the said face of the plate member (17; 117) by a silk screen printing process.