Abstract: Droplet deposition apparatus comprising first and second channels (82a, 82b), one end of each channel communicating with a single, common supply chamber (40) for supply of droplet liquid and the respective other ends of the first and second channels each communicating with a respective further supply chamber (88, 92) for supply of droplet liquid; each of said first and second channels having an opening (96a, 96b) for ejection of droplets therefrom; and actuator means being associated with each channel for effecting the ejection of droplets.

Abstract: A piezoelectric printhead or other droplet deposition apparatus has parallel liquid containing channels defined by a base and displaceable walls, and covered by a cover number. The channels each have at least one nozzle for ejecting droplets. Each nozzle may be disposed in the base, the cover then having two ink supply parts spaced lengthwise of each channel on opposite sides of the nozzle. Alternatively two longitudinally spaced nozzles may be provided in the base of each channel. The cover may have a conductive track corrected to wall-displacing electrodes, the points of connection being outside the channels.

Abstract: In droplet deposition apparatus comprising one or more independently actuable ink ejection chambers, electrical signals are applied to reduce variation in the temperature of the droplet fluid between chambers and with variations in droplet ejection input data. Short potential difference pulses, suitable for influencing the temperature of the droplet fluid in a chamber, can be generated by application of longer duration voltages to ink chamber actuation means.

Abstract: In ink jet printing, a UV curable undercoat is first deposited on a substrate. The ink and undercoat are cured together. The thickness of the undercoat varies inversely with the thickness of the ink, so that a flat print surface is achieved. Application of an undercoat may be disabled on text material, to preserve edge definition.

Abstract: A method of polarizing a portion of a monolithic piezoelectric actuator element for use in droplet deposition apparatus where the element has first and second portions, includes the steps of placing the first portion of the element at an equipotential and generating a polarizing electric field across the second portion between said first portion and a further conducting layer.

Abstract: A vacuum drum assembly for a printing machine comprises a drum having an array of passageways distributed along its length and around its periphery to permit air to flow from outside the drum to inside the drum in response to reduced air pressure inside the drum, and an array of valve members, each valve member being movable between a closed position in which that valve member restricts at least one of the passageways and an open position in which the restriction of that passageway or those passageways is reduced. The arrangement is such that, when a partial area of the drum is wrapped with a sheet of material, at least some of the valves for the passageways adjacent the edges of that area are open, and the valves for the passageways which are not covered by the sheet and are not adjacent the edges of that area are closed. The open area of the drum is regulated such that it is small in regions where there is no paper.

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 droplet deposition apparatus comprising one or more independently actuable ink ejection chambers, electrical signals are applied to reduce variation in the temperature of the droplet fluid between chambers and with variations in droplet ejection input data. Short potential difference pulses, suitable for influencing the temperature of the droplet fluid in a chamber, can be generated by application of longer duration voltages to ink chamber actuation means.

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 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 method for prevention of nozzle plate peel for inkjet printheads. The nozzle plate is bonded to the nozzle, with a layer of adhesive, and to a support, with a thicker layer of adhesive. This extra support prevents the peeling of the nozzle plate under the forces generated by, for example, a wiper blade passing over it. Spacers between the nozzle plate and support ensure the correct uniformity and constant thickness of the adhesive layer.

Abstract: An ink jet printhead has a body of PZT bonded to a base plate. Channels cut in the PZT form ink chambers which are actuated by applying voltages to electrodes on surfaces of the chambers. The base plate also carries IC's which contain the drive circuitry for actuating the ink chambers. To ensure reliable electrical interconnection between the chamber electrodes and the IC's, the electrodes and conducting tracks on the base plate are formed in a single step by depositing a conductive layer over both the PZT body and the base plate. The necessary pattern of electrodes and tracks can be achieved by masking or by selective material of conductive material.

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 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: The selected ink channels of a drop-on-demand ink jet printer are caused to expand and then contract, ejecting ink droplets by the application of unipolar voltages first to selected channels and then to non-selected channels. Further unipolar voltages, delayed in time by 2L/c and scaled by a pressure wave reflection coefficient r of the nozzle, effect prompt cancellation of residual pressure waves so that adjacent channels are ready for actuation with minimum delay.

Abstract: Nozzles for an ink jet printer are formed by laser ablation in a nozzle plate (24) which has previously been bonded to the body of the printer (16). The laser beam is caused to converge at a point in front of the nozzle plate (24) so that a nozzle is formed which tapers toward the outlet. First and second beam masks (72, 74) are established in front of a focussing lens with the masks being respectively conjugate in the lens with the nozzle inlet and outlet, which are of different shape. The nozzle has a central land (218) which controls the ink meniscus and avoids the ejected drop receiving a sideways kick from the nozzle wall.