Electrostatic spray nozzle system

An electrostatic spray nozzle comprising:

• an annular induction electrode made of an electrically conductive material and having a front end and a back end which are axially spaced from each other;
• means for forming a liquid into a liquid jet originating at a region which is axially rearwardly of the electrode and extending axially forwardly from said region toward the electrode and means for converting the liquid of the jet into a stream of liquid droplets moving axially forwardly through the annular induction electrode and for forming a gaseous slipstream moving along the electrode surface facing the stream and separating the last recited surface from the jet and the stream;
• means for maintaining the electrode at a selected electrical potential with respect to said liquid;
• and
• a hollow housing made of an electrically insulating material and surrounding the annular electrode, said housing having a front wall disposed forwardly of the front end of the electrode and means defining a spray orifice in said front wall which is substantially coaxial with the annular electrode.

An electrostatic spray nozzle comprising:

• a base having an axially extending, central conduit for receiving liquid under pressure at its back end and for issuing a forwardly directed liquid stream at its front end, said base further having a separate, generally axially extending conduit for receiving air under pressure at its back end and for issuing at its front end a forwardly converging air stream for interacting with and atomizing said liquid stream;
• a housing fixedly secured to the base and having an axially extending passage coaxial with the liquid conduit of the base, said passage having a back portion communicating with the air and liquid conduits to receive the streams issuing from the conduits and having a front portion extending forwardly of said back portion;
• an annular induction electrode disposed within the housing, coaxially with the passage, said electrode having a front end which is rearwardly of the front portion of the passage but forwardly of the front ends of the conduits and a rear end which is forwardly of the front end of at least the liquid conduit;
• the base and the back portion of the passage enclosing a droplet forming region where the air and the liquid streams interact to form a forwardly directed droplet stream combined with an air slipstream separating the electrode from the liquid and droplet streams and maintaining the electrode free of droplets and of liquid;
• and
• said housing being made of an electrically insulating material.

A method of forming a stream of electrostatically charged liquid droplets comprising the steps of:

• providing a liquid jet and converting the liquid jet into a stream of finely divided liquid droplets moving along a selected direction;
• inductively charging the droplets of said droplet stream with a toroidal electrostatic field having lines of force emanating from an annular induction electrode and terminating at the droplet stream, said toroidal field being coaxial with said selected direction;
• and
• enclosing said induction electrode in an electrically insulating housing having an orifice coaxial with the selected direction for allowing the charged droplet stream to exit from the housing, said annular electrode and the toroidal electric field produced thereby being spaced inwardly into the housing from said orifice and said electrode being spaced forwardly of the origin of the liquid jet.