Abstract: An electrostatic spraying device for use in spraying inter alia personal care and personal hygiene products comprises an outlet (94) from which the product issues in the form of an electrostatically charged spray and a control member (60, 60a) for attenuating the potential gradient in the vicinity of the outlet (94) to such an extent that spraying is suppressed until the device is brought to within a predetermined distance from a site to be spayed.

Abstract: A method and device (20) for spraying particulate materials in which a high voltage is applied to a mass of the particulate material so as to cause particles to issue from the mass. High voltage from a source (16) is applied to a mass of material (36) stored in a container. A surface of the mass (36) is exposed to the surroundings and the applied voltage is conducted through the bulk material to particles located at the exposed surface which are thereby projected as an electrically charged spray from the mass under the influence of the electric field substantially without any accompanying corona discharge.

Abstract: A high voltage generator is provided for use in applications where current demand is low but a high voltage is required. The generator comprises an array of photosensitive elements, such as an array of photovoltaic elements produced by laser scribing or etching of a wafer of material conventionally used for solar cells, the number of elements employed and their interconnection being such that a high voltage output of at least 1 kV is obtained.

Abstract: The present invention provides an electrostatic spraying device which includes a primary charge return path between the device and the target to be sprayed and circuitry for warning the operator of potentially hazardous spraying conditions. More particularly, the present invention includes circuitry for warning the operator of conditions wherein the primary charge path is inadequate and other conditions in which the return of spray current via the primary charge path is affected.

Abstract: An electrostatic spraying device is disclosed having a container (16) for the liquid to be sprayed and a capillary structure (22) extending into the container. To maintain a substantially constant liquid level at the location where liquid is drawn into the capillary structure, the container is partitioned into two chambers, one (68) of which is isolated from atmosphere and the other (66) of which is in communication with atmosphere. The capillary structure (22) extends through one chamber and the arrangement is such that the liquid level at the location where the capillary structure communicates with the liquid is maintained substantially constant over a wide range of variation of the liquid level within the other chamber. The upper end of the capillary structure may be provided with an oblique end face (50; 70, 72) to facilitate dispersal of the spray into the surroundings.

Abstract: An electrostatic spraying device for spraying liquids comprises a hollow capillary structure having a convoluted inner surface, one end of which contacts a reservoir of an electrostatically sprayable liquid preferably having a viscosity from 1 to 20.times.10.sup.-6 m.sup.2 /s and a volume resistivity from 2.5.times.10.sup.6 to 5.times.10.sup.8 ohm cm, the other end of which terminates in an atomization tip, and means for applying high voltage to the liquid in order to cause the liquid at the atomization tip to break up into a plurality of electrostatically charged droplets. Cartridges for use in the electrostatic spraying device are also described.

Abstract: An electrostatic spraying device for use in spraying liquids having resistivities of the order of 5.times.10.sup.6 ohm.multidot.cm and viscosities of the order of 1 Poise at a spraying rate up to at least 4 cc/min (especially paint formulations) is provided with an annular shroud (112) of semi-insulating material (e.g. bulk resistivity of the order of 10.sup.11 to 10.sup.12 ohm.multidot.cm) which is electrically connected to a high voltage generator (126) for supplying high voltage to liquid emerging at the outlet of the nozzle (114). In this way, a voltage is established on the annular electrode (126) which is of the same polarity, and substantially the same magnitude, as the voltage applied to the liquid thereby modifying the potential gradient in the immediate vicinity of the nozzle outlet so as to allow the use of the high voltage needed to effect efficient spraying of liquids having the specified resistivity and viscosity at flow rates up to at least 4 cc/min.

Abstract: A novel semiconductor switching device for use in high voltage applications (typically ranging from 5 kV up to about 50 kV) makes use of the well-known effect of reverse conduction in silicon diodes when exposed to light. Hitherto, photodiodes have been commercial available for relatively low voltage applications. The device disclosed herein is implemented by a high voltage diode having a series of semiconductor junctions and a light emitting diode operable to irradiate the junctions to render the high voltage diode conducting in the reverse bias direction. The switching device finds application in electrostatic spraying devices where the current demands are relatively small, eg up to about 2 .mu.A.