GB744547A - Improvements in or relating to aerosols - Google Patents

Abstract

744,547. Aerosols. HURST, H. July 27, 1954 [July 27, 1953; July 30, 1953], Nos. 20768/53 and 21158/53. Class 81(1). In a method for the thermal production of an aerosol of an insecticide, bactericide or like active material, a solution or dispersion of the active material in a more volatile liquid is caused to impinge onto a surface, heated to a temperature above the boiling point of the vehicle, of an enclosed chamber having one or more outlets for the aerosol. The cross section of the heating chamber may be restricted so that the outlet or outlets or the chamber itself are periodically blocked by droplets of liquid and the aerosol is ejected periodically in pulses. In one modification of the apparatus for carrying out the invention an aluminium container 10 is filled with a solution of pyrethrins in a mixture of methyl and ethyl alcohols which passes by gravity through a copper tube 15, sweated into a thicker horizontal copper tube 17 acting as a heating chamber within which is a bimetallic strip 20, which restricts the entry of insecticide into the chamber by means of a conical plug valve 21, and surrounded by a heating element 13. When the current is switched on the chamber is heated and the bimetallic strip 20 is deformed so that at a critical temperature the plug 21 moves downwards and insecticide descends into the heating chamber, where the volatile alcohol components vaporise and build up a pressure within the chamber so that the resultant aerosol is emitted in a series of puffs through an orifice or nozzle 22 at the end of the chamber. When the heating current is switched off the plug 21 gradually closes and restricts the flow of insecticides.