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 co-fired laminate (10) for use in printheads for drop-on-demand ink jet printers has two inner layers (12, 14) of piezoelectric material which are thickness poled in opposite senses, two outer layers (11, 15) of inactive material and a fifth layer (13) disposed between the inner layers which is electrically insulating under the printhead operating conditions and conductive under the poling conditions of the inner layers. The fifth layer preferably is an N.T.C. material with its critical temperature between the operating and poling temperatures. After poling of the inner layers further manufacture of the printhead from one side thereof can be effected as described.

Abstract: A method of multi-tone printing employs a drop-on-demand printing apparatus 100 for depositing ink droplets from an array of channels 104 on printing element areas of a substrate 111 which is movable relatively to said apparatus. The channels length and nozzle location and dimensions afford each channel with a high longitudinal resonant frequency and electrically actuable means 110,112,114,116,118 supply energy pulses to a selected band of channels at or near the resonant frequency of the channels to deposit from each selected channel in the corresponding printing element area of the substrate a number of drops equal to the number of pulses applied thereto, the number of pulses applied being dependent on the tone of printing required. Droplet ejection from even numbered channels is in anti-phase at the resonant frequency with droplet ejection from odd numbered channels.

Abstract: A method of operating a pulsed droplet deposition apparatus, e.g. a drop-on-demand ink jet printer, having a droplet liquid chamber (16) with which a nozzle (18) communicates for expulsion of droplets (12) from the chamber, droplet liquid replenishment means (20) connected to the chamber and energy pulse applying means for imparting pulses of energy to the droplet liquid in the chamber, employs, to increase the volume of droplets expelled by respective energy pulses, a droplet liquid having high viscosity at low shear rate and low viscosity at high shear rate, the liquid relaxation time constant being of the same order or greater than the period of pulses applied to the liquid and the characteristic time of the liquid in the nozzle being of the same order or less than the period of the pulses.

Abstract: A method of multi-tone printing employs a drop-on-demand printing apparatus for depositing ink droplets on printing element areas of a substrate which is movable relatively to the apparatus. The droplets are deposited from an array of channels on the substrate which is movable relatively to the channels. The channels length and nozzle location and dimensions afford each channel with a high longitudinal resonant frequency and energy pulses are supplied to selected channels at or near the resonant frequency of the channels to deposit from each selected channel in the corresponding printing element area of the substrate a number of drops equal to the number of pulses applied thereto, the number of pulses applied being dependent on the tone of printing required. Single channel and color versions of the invention are also disclosed.

Abstract: A method of manufacturing one or more nozzles for an ink jet printhead initially comprises bonding a nozzle plate to the ink ejection end of the printhead. A mask is then secured in contact with the nozzle plate, the mask having a plurality of apertures each defining a respective nozzle exit. Laser radiation applied to the mask exposes the areas defined by the apertures to ablate the plate material between the nozzle exits on the external surface of the plate and corresponding nozzle inlets on the opposite surface of the plate. The assembly comprising the printhead, plate and mask is rocked during the exposure step to increase the area of the nozzle inlet relative to its outlet. Also, prior to the nozzle formation step, one or more ink troughs may be provided for supplying an external source of ink for each nozzle. The ink troughs, which may be formed using laser ablation techniques similar to those used in the formation of the nozzles, facilitate a continuous, positive flow of ink through the nozzles.

Abstract: A pulsed droplet ink jet printer has at least one channel communicating with a nozzle. The side wall of the channel is formed as a shear mode piezo-electric actuator comprising an unpoled crystalline material. Electrodes applied to the actuator enable an electric field to be applied such that the actuator moves in transversely of the field to change the liquid pressure in the channel and thereby eject a droplet through the nozzle. The actuator can be made in two parts so as to deform, in cross section, to a chevron formation.

Abstract: A pulsed droplet ink jet printer has at least one channel communicating with a nozzle. The side wall of the channel is formed as a shear mode piezo-electric actuator. Electrodes applied to the actuator enable an electric field to be applied such that the actuator moves in the direction of the field to change the liquid pressure in the channel and thereby eject a droplet through the nozzle. The actuator can be made in two parts so as to deform, in cross section, to a chevron formation.

Abstract: A multi-channel array, pulsed droplet ink jet printer comprises a plurality of channels each communicating with a respective nozzle. A side wall of each channel is formed as a shear mode piezo-electric actuator. Electrodes applied to the actuators enable electric fields to be applied such that the actuators move laterally in the direction of the field to change the liquid pressure in the channels for effecting droplet ejection through the channel nozzles. The actuators can be made in two parts so as to deform, in cross section, to a chevron formation.

Abstract: A method for testing body components of pulsed droplet deposition apparatus comprises applying a variable frequency voltage to the electrodes of each of a number of selected channel wall elements. The resulting impedance variations are used to determine the natural frequencies of the selected wall elements which, in turn, are used to determine whether the compliance ratios of the selected wall elements and the droplet liquid to be used therewith lies within a desired range of values.

Abstract: A housekeeping manifold is provided at the end of a row of ejector apertures of a drop-on-demand printhead module. The housekeeping manifold includes upper and lower parts disposed on opposite sides of the row of ejector apertures, a trench extending between the manifold parts through which ink drops from the ejector apertures are discharged, openings between the manifold parts and the trench and a ducting arrangement for supplying environmental fluids to or exhausting such fluids from the region of said apertures by way of the manifold parts and trench.

Abstract: A drop-on-demand ink drop printhead is mounted fixed in a printer for selectively printing drops of ink in a print line. The printhead comprises a plurality of stacks of like print modules arranged in side-by-side relationship to form a number of laterally offset module layers. Each of the modules includes at least one group of uniformly laterally spaced ink ejectors, the groups in each layer being laterally spaced by the same amount such that drops from overlapping portions of two or more of the groups interleave to form a segment of the print line. Make-up ink and air supply ducting arrangements are provided for the modules in each stack.

Abstract: A pulsed droplet ink jet printer has relatively long thin ink channels extending in parallel between an ink manifold 13, and a nozzle plate 5 providing a nozzle 6 for each channel. Side walls 11 may be formed substantially entirely of piezo-electric material so as to be displaceable transversely into a selected channel on the application of an electric field. This transverse displacement produces an acoustic wave in the channel which results in the ejection of an ink droplet. The side walls may deflect in shear mode to a cross-section of chevron formation. Usefully, it is arranged that both side walls adjoining the selected channel are displaced inwardly of the channel to cooperate in droplet ejection. Under this arrangement, the channels are assigned alternately to first and second groups of channels, only one group of channels being capable of actuation at any one instant.

Abstract: A pulsed droplet ink jet printer has at least one channel communicating with a nozzle. The side wall of the channel is formed as a shear mode piezo-electric actuator. Electrodes applied to the actuator enable an electric field to be applied such that the actuator moves in the direction of the field to change the liquid pressure in the channel and thereby eject a droplet through the nozzle. The actuator can be made in two parts so as to deform, in cross section, to a chevron formation.

Abstract: An ink jet"drop-on-demand" printer has a number of parallel channels each containing ink. A thread of mercury extends longitudinally of each channel or pair of channels and is connected for electrical current flow. A magnetic field is applied orthogonally to the channel plane such that current flow in a selected channel causes electromagnetic deformation of the mercury thread. This leads to a pressure pulse in the ink causing ejection of an ink droplet. With a mercury thread shared between a pair of channels, current in the opposite sense results in droplet ejection from the opposite channel of the pair.

Abstract: An ink jet array printer has at least one row of printing guns. The guns deposit drops which are charged and deflected for printing on a printing surface moving relatively to the printer in line sections which together form a transverse printing line. The charging of the drops is effected by applying to the charge electrode of each gun, under the control of printing information, a periodic voltage waveform of sufficient period to span a raster of successively formed drops which are employed for printing the corresponding line section, the printing lines being successively formed at the frequency of the voltage waveform.

Abstract: A loom in which each warp yarn passes through a retraction region and a shedding region, and in which means are provided for creating gaseous fluid flow along each warp yarn so that the yarns, or those that are not otherwise restrained, are moved to form a loop in the shedding region, the loops, or selected ones of them, being separated from the warp yarn sheet by gaseous fluid flow to form a shed, and means are provided for mechanically displacing portions of the yarns in the retraction region to move the yarns longitudinally into a path of predetermined length so as to draw the yarns into tension in the shedding region to close the shed. The means for drawing the yarns into tension may also be employed to draw the fell of the woven fabric against a fixed reed to beat up the inserted weft yarn.

Abstract: A pulsed droplet ink jet printer has relatively long thin ink channels extending in parallel between an ink manifold 13, and a nozzle plate 5 providing a nozzle 6 for each channel. Side walls 11 may be formed substantially entirely of piezo-electric material so as to be displaceable transversely into a selected channel on the application of an electric field. This transverse displacement produces an acoustic wave in the channel which results in the ejection of an ink droplet. The side walls may deflect in shear mode to a cross-section of chevron formation. Usefully, it is arranged that both side walls adjoining the selected channel are displaced inwardly of the channel to cooperate in droplet ejection. Under this arrangement, the channels are assigned alternately to first and second groups of channels, only one group of channels being capable of actuation at any one instant.