In an electrically actuatable fuel-injection valve for internal combustion engines, a piezoelectric oscillator (radial oscillator 11) which is provided with electrodes has at least one fuel-receiving chamber (12). The chamber (12) is in communication with the fuel feed path (constant-volume chamber 20) and an ejection opening (bore 17). The oscillator (11) is mounted in a block (18) out of which the fuel feed path (constant-volume chamber 20) is also formed. Furthermore, a high-voltage generator (35) is located, electrically shielded from the outside, within the block (18), which consists of metal. The high-voltage generator is connected to the electrodes of the piezoelectric oscillator (11) via feed lines (14, 15) which are conducted within the block (18).

An atomizer head for use with a spray gun has a centrally located paint spray orifice with an essentially elliptical cross-section and a pair of compressed air output orifices offset from the paint spray orifice. The output air forms a screen, with an elliptical cross-section, that prevents the paint spray from breaking up.

A spray arrangement including means to form and direct a spray of liquid droplets and means to apply an electrostatic charge to droplets in said spray, said charge applying means including an insulating body to support a spray-charging electrode in association with the spray-forming means, the spray-forming means [10] forming the spray hydraulically, the body [20] having a smoothly-constricted bore [26, 27, 28] for the free passage of spray with the electrode [23] housed to expose only inward-facing electrode surface [28] as the constriction to passing spray [40] for the acquisition of charge therefrom, the bore surface turning back upon itself [29] as it expands beyond the constriction to form an end of the body, the end of the body where the surface turns back upon itself [29] and the part of the bore remote from said end being formed to assist the shedding of liquid [22, 51, 52]. The arrangement is suitable as a dairy sprayer to direct charged spray upwardly from said turned-back end on to the teats and udder of a dairy animal such as a cow, ewe or goat.

Electrostatic spraying apparatus employs a concealed electrode at a low potential (relative to that used in conventional apparatus) to form an induced charge on a thin layer of liquid. Subsequent mechanical atomization of the charged layer produces a spray of charged droplets. The thin layer is produced by centrifugally spreading an inlet flow and atomization may also be achieved by rotation. An air flow is arranged to sweep the charged droplets out of the field of the electrode and a baffle, in which the electrode is embedded, is formed to control the direction of emergence of the spray from the nozzle.

A light-weight, portable power pack for supplying a high voltage output to an electrostatic spray gun from a low voltage input is disclosed. The power pack is mounted on and forms a part of the spray gun and is detachable therefrom for replacement purposes. The power pack comprises a voltage multiplier circuit for converting a low voltage DC to a high voltage DC for induction charging of material discharged from the spray gun, the circuit being encapsulated in an epoxy resin material to provide a suitable mounting case therefor. The case is molded into a suitable shape and is attached, in one embodiment, to the bottom portion of the barrel of the gun by means of screws, bolts or the like, the power pack being provided with external contacts which serve to engage corresponding contacts on the spray gun to provide electical contact through the gun to the power source, which may be a battery pack carried by the operator, and to the inductive charging device for the spray gun. In another embodiment, the power pack may be mounted upon a detachable accessory such as a gas shroud forming chamber which is in turn mountable on the forward end portion of the spray gun barrel.