Automatic shutoff dispensing nozzle venturi

Claim 1

A variable venturi for an automatic shutoff nozzle including a body having a cylindrical throat bore and a conical bore smoothly merging with said throat bore, said conical bore being disposed on the same axis as said throat bore, a valve to close said throat bore to prevent communication between said throat bore and said conical bore, the outer surface of said valve and the surface of said conical bore diverging from each other away from said throat bore to provide an annular diverging passage therebetween when said valve is open, said body having an enlarged area in said body formed in said conical bore, said enlarged area being in communication with said conical bore to allow expansion of liquid flowing from said throat bore to said conical bore to create a reduced pressure area in said enlarged area, said enlarged area having its surface furthermost from said throat bore located no greater than 0.2 of the diameter of said throat bore along the wall of said body defining said conical bore from the intersection of said throat bore and said conical bore, and said body having means to provide communication between said enlarged area and the exterior of said body for communication with the atmosphere, the flow of liquid through the diverging annular passage between said valve and said conical bore when said valve is open cReating a suction effect in said communicating means.