An electrostatic, coating-dispensing apparatus includes an electrode upon which an electrostatic potential is impressed. The electrostatic potential is developed by a switching circuit, autotransformer and voltage multiplier from rectified line voltage. The entire apparatus is housed in a hand-held applicator to which line voltage is supplied. In one embodiment, suitable for the hobbyist, the apparatus includes a socket defined at one end thereof for interchangeably receiving containers holding various colors or types of coating material. Each container includes an electrode for contacting the first-mentioned electrode. The containers are shaped to fit snugly into the socket to hold the two electrodes in contact. An outer end wall of each container has a mesh portion through which charged particles of coating material from the interior of the container pass when the apparatus is activated. In another embodiment suitable for industrial applications, the coating material and any other necessary supplies, such as compressed air, are provided through hoses to the dispensing apparatus. The electrostatic potential supply is sufficiently compact that it can be housed within the hand-held dispensing apparatus.
An improved electrostatic spray gun wherein the power pack for transforming a low voltage electrical signal from an external source to a high voltage signal for application to the gun electrode is wholly contained within the handle of the gun. The gun includes multiple interchangeable barrels for enabling the gun to spray airless atomized liquids, or air spray atomized liquid, or air-entrained solid particulate materials.
An electrostatic spraying device is designed in such a way that potential surface leakage paths (FIG. 1b) along which current may leak from the HT generator (2b) are sufficiently long to allow the use of a generator having a smaller than conventional maximum current output.
An electrostatic spraying apparatus is in the form of a device suitable for hand held use. The device uses a high voltage generator of the rectified pulsed type and includes an earth return path which is completed via the operator through a contact (38) associated with the hand grip (4) of the device. Resistance (36), typically of the order of 50 megohm, suppresses pulsed electrical sensations that may be experienced by the operator in the event that the nozzle (12) is contacted with an earthed object, and the nozzle (12) is designed so that the liquid therein presents, by virtue of the length and cross-sectional area of a liquid conducting passage(s) in the nozzle, a high resistance between the voltage generator (26) and the nozzle thereby reducing the energy that can be drawn to earth by electrical discharge.
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.
An electrostatically aided coating dispensing system in which the high distributed capacitance of a high voltage cable for connecting the high voltage supply to dispensing device is entirely eliminated.
