Injector pump

An in-line, two-stage, variable-bypass injector pump for controlling admixing a secondary fluid to a main fluid, comprising:

• a housing connectable into a pipe line carrying said main fluid;
• a main venturi extending along the central axis of said housing and comprising an entrance, throat and exit portion,
• a secondary venturi off center but substantially parallel to said central axis, comprising an entrance, throat and exit portion which exit portion leads into the throat portion of said main venturi;
• a connector, one end of which leads into the throat portion of said secondary venturi and the other end of which is connectable to a source of said secondary fluid;
• at least one passageway located off center with respect to said main venturi and designed to permit a variable proportion of said main fluid to flow from one end of said housing to the other end thereof, while bypassing said main venturi, and
• shutter means to control said bypassing flow between a maximum and zero flow, wherein said shutter means are constituted by a rotatable disc-shaped plate located in the throat region of said main venturi, having a central bore appropriate to the diameter of the venturi at said region, and being provided with at least one opening located off center with respect to said main venturi and substantially identical and alignable with said bypass-flow passage way,
• wherein, by selectively creating a misalignment between at least two different portions of said passage way, a variable constriction is produced in said passage way, which constriction, when maximum, results in zero bypass flow and, when zero, results in maximum bypass flow.