Abstract: A process for the production of solid particles, characterized by the solidification in flight of an electrically charged spray of fluid droplets of narrow particle size distribution, and an apparatus for that process comprising a sprayhead with a channel for the fluid communicating with an outlet; means for subjecting the fluid to an electrical field such that the fluid will move from the sprayhead under the influence of the field to produce a spray of the fluid, the means including means for applying a first potential to the fluid; an electrode mounted spaced from but adjacent to the sprayhead with means to apply a second potential to that electrode; and a spray chamber, so positioned that in use the sprayhead delivers the spray to the chamber interior, and provided with means to apply a third potential to the chamber, and so dimensioned and arranged that in use the majority of the spray droplets solidify before impinging on any surface of or within the chamber.

Abstract: Electrostatic spraying apparatus and process for spraying liquids which form a coalescent resistant surface in flight in a particular environment to produce a powder or granular material. The process involves delivering a liquid to a spraying site of an electrostatic spray head; making contact with the liquid via an electrically conducting or semiconducting liquid contacting surface; charging the liquid contacting surface to a high voltage of one polarity relative to a reference surface to intensify the electric field strength at the spraying site sufficiently that the liquid at the spraying site is drawn out preponderantly by electrostatic forces into at least one cone from which a corresponding ligament issues and breaks up into a spray of electrostatically charged droplets; providing the environment in a space sufficient that droplets from the spray head form, in flight, particles having a substantially coalescent resistant surface; and collecting the particles so formed.

Abstract: An apparatus and process for spraying liquids wherein liquid emerging from a sprayhead is subjected to an electrical field sufficiently high for the liquid to be drawn from the sprayhead in the form of one or more filaments. The filament or filaments become unstable and subsequently break up into droplets. A stream of gas is caused to flow through the region of the high electrical field, the gas flowing in a direction parallel or substantially parallel with the direction in which the liquid emerges from the sprayhead. Droplets are thus removed from the region and a built-in in space charge is reduced.

Abstract: An electrostatic pump or pumping liquids having a resistivity in the range of 10.sup.10 to 10.sup.7 ohm cm has a pump housing. The pump housing includes a passageway through which the liquid is pumped, and a single injection electrode disposed upstream of the passageway. The electrode has a sharp electrically-conducting tip. A constriction in the region of the tip is shaped to conform to the surface configuration of the tip so that the liquid flows pass the tip in a laminar nonturbulent fashion through an orifice of reduced cross-section. The constriction is so dimensioned as to provide a high resistance path. A chamber is disposed downstream of the constriction and is of larger cross-section than the constriction. A discharged electrode is disposed in the chamber and is separated from the injection electrode by the chamber and the constriction. The injection and discharge electrodes are coupled to a high voltage generator to maintain an electric potential between the electrodes on the order of kilovolts.

Abstract: A spray malfunction detector system for electrostatic spraying apparatus having a sprayhead connectable to a high voltage source and for directing spray of charged particles of fluid towards an earthed target. The system comprises an earth circuit from the earthed target, a by-pass electrode located in the vicinity of the sprayhead and maintained in use at such a potential as to attract corona discharge from the sprayhead, and a current detector located in the earth circuit between the earthed target and any junction in the earth circuit and by which corona discharge joins the earth circuit from the by-pass electrode.