Abstract: An ink jet printer ink is provided in the form of a non-aqueous dispersion of colorant in a diluent and containing a dispersant for the colorant and which yields print having no discernible odor. The diluent comprises more than 50% by volume of white oil and the dispersant, which is employed in an amount of at least 20% by weight of the colorant, comprises at least one compound having both a long chain aliphatic group and at least one &agr;, &bgr;-dicarboxylic acid moiety, e.g. a polyisobutylene succinimide.

Abstract: A vacuum drum assembly for a printing machine has a drum with an array of passageways distributed along its length and around its periphery to permit airflow from outside the drum to inside the drum in response to reduced air pressure inside the drum. An array of valves are movable between a closed position in which that valve restricts at least one of the passageways and an open position in which the restriction of the same passageways is reduced. When a partial area of the drum is wrapped with a sheet of material, at least some of the passageway valves adjacent the edges of that area are open, and the valves for the passageways not covered by the sheet and not adjacent the edges of that area are closed. The drum open area is regulated to be small in regions where there is no paper. Accordingly, the open area of the drum is adapted to the paper shape and size and the paper position on the drum, while minimizing the required suction flow.

Abstract: In a method of colour printing using arrays of threshold value for interpolating between grey levels, the threshold values for each of the colours are provided by defining rows of threshold values, with each row having the same repeating sequence but offset. The repeating sequences are different for each colour but the offset is the same for all colours. The arrays best take the form Tijc=(i*pc−j*qc)%(rcS).

Abstract: A droplet on demand inkjet apparatus utilizing a piezoelectric actuator arranged so as to deflect in shear mode, a method of ink jet printing, and a method of manufacturing an ink jet printing apparatus are disclosed. The apparatus is formed of a plurality of laminated plates arranged so as to define an ink chamber. The actuator forms one side of the chamber and deflects towards a nozzle formed in a nozzle plate which provides the opposite side of the chamber. An interconnect layer acts as the substrate and has orifices to allow the tracks to the drive chip to pass through. On the opposite side of the interconnect layer is the piezoelectric sheet. Electrodes are provided between the interconnect layer and the piezoelectric sheet. The piezoelectric sheet is carved, drilled or molded so as to provide parallel ink channels and a circular depression with a raised central reservation. The piezoelectric sheet is bonded to the interposer plate or ground electrode which in turn is bonded to the nozzle plate.

Abstract: A ceramic piezoelectric ink jet print head having at least one channel with walls coated with a multi-layer coating including an electronic barrier layer and an electrically conducting layer where the electric barrier layer is disposed between the channel well and the electrically conducting layer.

Abstract: Method of operating an inkjet printhead for printing on a substrate; the printhead having a chamber communicating with a nozzle for ejection of ink droplets and with a supply of ink; the printhead further comprising electrically actuable means associated with the chamber and actuable a plurality of times in accordance with print tone data, thereby to eject a corresponding number of droplets to form a printed dot of appropriate tone on the substrate; the method comprising the steps of applying a plurality of electrical signals to the electrically actuable means in accordance with the print tone data, the time delay between application of successive signals being such that any variation in the average velocity at which corresponding droplets travel to the substrate to form said printed dot remains below that which would lead to defects in the printed image detectable by the naked eye, regardless of the number of said droplets ejected to form said printed dot.

Abstract: A drop-on-demand multi-tone printing apparatus has a series of channels arranged to receive ink from a source. Each channel has a respective ink outlet. Each adjacent pair of the channels is separated by a respective dividing wall, and each dividing wall is movable in response to a respective pulsed electrical signal to apply pressure pulses to the respective pair of the channels, whereby ink can be ejected from the outlets and deposited onto a recording medium. A respective pulsed electrical signal is developed for each channel in dependence upon whether ink is to be ejected from that channel, the signals for adjacent pairs of the channels temporally overlapping each other and not being in phase with each other.

Abstract: A process for the selective passivation of the channel walls of a channelled ink-jet printhead component by the chemical vapor deposition of a passivant coating, the process comprising mounting the component in a support in registration with a datum location therein, the support having masking means for masking selected areas of the component, and depositing the passivant coating on unmasked portions of the channel walls.

Abstract: Ink jet printer dispersion inks are provided which contain a dispersant having basic or acid groups and a non-destabilizing amount of a neutralizer for said groups. The inks exhibit improved non-wetting characteristics leading to lengthening of the duration of periods of continuous printing that can be achieved before cleaning or replacement of the nozzle plate of the ink jet print head is required.

Abstract: A drop-on-demand piezo-electric printhead has channel walls defined by piezo-electric material (10) with electrodes (26) along the length thereof. In portions of the channels which are open to an ink supply conduit, the piezo material is locally disabled, e.g. by reducing the width of the electrode or by interposing a material (40) of lower dielectric constant between the electrode and the piezo material. A lower capacitive load results.

Abstract: A nozzle in a nozzle plate for an inkjet printhead is formed by directing a laser beam at a nozzle plate. Accurate control of the divergence of the beam is achieved by splitting the beam into sub-beams, each sub-beam having divergence with an origin lying apart from the point at which the beam is created by splitting, and thereafter recombining the sub-beams. Greater accuracy in the taper and inlet shape of the manufactured nozzle is thereby obtained.

Abstract: Drop-on-demand ink jet printing apparatus comprises a nozzle on a nozzle axis; an ink chamber communicating with the nozzle, a piezoelectric actuating structure, said structure extending around the nozzle axis and extending in the direction of the nozzle axis; an actuating surface facing the nozzle, said structure being actuable to move said actuating surface in the direction of the nozzle axis to effect droplet ejection through the nozzle; and electrodes for applying an actuating electric field to the actuating structure.

Abstract: A drop-on-demand piezo-electric printhead has channel walls defined by piezo-electric material (10) with electrodes (26) along the length thereof. In portions of the channels which are open to an ink supply conduit, the piezo material is locally disabled, e.g. by reducing the width of the electrode or by interposing a material (40) of lower dielectric constant between the electrode and the piezo material. A lower capacitive load results.

Abstract: A process for the selective passivation of the channel walls of a channelled ink-jet printhead component by the chemical vapor deposition of a passivant coating, the process comprising mounting the component in a support in registration with a datum location therein, the support having masking means for masking selected areas of the component, and depositing the passivant coating on unmasked portions of the channel walls.

Abstract: A method of operating an inkjet printhead for printing on a substrate, the printhead having an array of channels; a series of nozzles which communicate respectively with said channels for ejection of droplets therefrom; connection means for connecting the channels with a source of ink; and electrically actuable means associated with each channel and actuable a plurality of times in accordance with print tone data, thereby to eject a corresponding number of droplets to form a printed dot of appropriate tone on the substrate, the method comprising the steps of: applying one or a plurality of electrical signals to the electrically actuable means associated with a channel in accordance with the print tone data, the duration of each signal being chosen such that the velocity of the corresponding ejected droplet is substantially independent of (a) whether or not channels in the vicinity of said selected channel are similarly actuated to effect drop ejection simultaneously with drop ejection from said selected chann

Abstract: To allow accurate positioning relative to a printer mechanism, a printhead is provided with a reference surface formed on a reference member. The reference member is attached to the base of the printhead but positioned with reference to a nozzle of an ink ejecting unit mounted on the base member. This obviates the need for the base member to be manufactured to narrow tolerances.

Abstract: A process for the selective passivation of the channel walls of a channelled ink-jet printhead component by the chemical vapor deposition of a passivant coating, the process comprising mounting the component in a support in registration with a datum location therein, the support having masking means for masking selected areas of the component, and depositing the passivant coating on unmasked portions of the channel walls.

Abstract: A nozzle in a nozzle plate for an inkjet printhead is formed by directing a laser beam at a nozzle plate. Accurate control of the divergence of the beam is achieved by splitting the beam into sub-beams, each sub-beam having divergence with an origin lying apart from the point at which the beam is created by splitting, and thereafter recombining the sub-beams. Greater accuracy in the taper and inlet shape of the manufactured nozzle is thereby obtained.

Abstract: An ink-jet head is formed by partitioning a plurality of ink chambers made from piezoelectric members from each other. Ink chambers which emit ink and dummy ink chambers which do not emit ink are arranged alternately, and ink is supplied to the ink chambers from a common ink chamber. This ink head is used to sequentially perform emission of an ink drop from the ink chambers for a plurality of times, to achieve gradation printing, while the emission speed of the ink drops is gradually increased such that ink drops emitted later are merged with ink drops emitted earlier thereby to form a one-dot liquid drop. In this case, where adjacent ink chambers with a dummy ink chamber inserted therebetween are simultaneously driven, timings of drive pulse voltages q1 and q2 applied to both of the adjacent ink chambers are shifted from each other such that the pressure in one of the adjacent ink chambers is decreased when the pressure in the other of the adjacent ink chamber is increased.

Abstract: Ink jet printer dispersion inks are provided which contain a dispersant having basic or acid groups and a non-destabilizing amount of a neutralizer for said groups. The inks exhibit improved non-wetting characteristics leading to lengthening of the duration of periods of continuous printing that can be achieved before cleaning or replacement of the nozzle plate of the ink jet print head is required.