Apparatus for producing a spray of droplets of a liquid

An inhaler for producing a spray of droplets of a liquid to be inhaled, comprising:

• a housing;
• a shield electrode mounted within said housing so as to define with the walls of said housing a chamber within the housing, said sheild electrode having an orifice defined therethrough;
• at least two apertures defined in said walls and spaced apart so as to define an air passage through the chamber so that droplets in the chamber can travel out of the chamber while air enters the chamber;
• a spraying edge;
• means for supplying a liquid to be sprayed to the spraying edge, said spraying edge directing sprayed liquid toward the orifice in the shield electrode, said spraying edge being spaced from said shield electrode and defined exteriorly of said chamber so that liquid sprayed from the spraying edge can issue into the chamber through said orifice in said shield electrode;
• means for producing a charge to a high potential of one polarity relative to the shield electrode in liquid at the spraying edge, to define an electric field between the spraying edge and the shield electrode sufficient to cause the liquid to issue from the spraying edge as at least one cone from which electrostatic forces repel through the orifice a ligament which breaks up into a spray of charged droplets;
• a sharp discharge electrode mounted within said chamber and spaced from the shield electrode, said sharp discharge electrode being defined on the opposite side of the shield electrode from the spraying edge;
• means for charging the discharge electrode to a high potential of an opposite polarity relative to the shield electrode, so as to produce a corona to discharge the spray, the shield electrode being of sufficient overall dimensions and having a sufficiently small orifice to define a means for shielding the edge and the cone of liquid from the corona.