Ultra-high vacuum force, low air consumption pumps

A multi stage ejector assembly comprising a solid elongate housing, a longitudinal cylindrical bore through said housing comprising a first venturi pump having a first converging-diverging venturi inlet nozzle opening through a first vacuum chamber in said cylindrical bore into the converging entrance of a first exit passage which opens through a second vacuum chamber into a second exit passage communicating with an outlet end of the cylindrical bore, first and second transverse bores inwardly from a side of the housing and each opening into said cylindrical bore at said first vacuum chamber, and a third transverse bore inwardly from a side of the housing and opening into said cylindrical bore at said second vacuum chamber, said first transverse bore comprising a second venturi pump having a second venturi inlet nozzle having an air flow consumption which is from about 5 to 15 times smaller than the air flow consumption of said first venturi inlet nozzle, said second venturi inlet nozzle opening through a maximum vacuum chamber into a converging-diverging venturi exit passage which opens into said cylindrical bore at the first vacuum chamber of the first venturi pump adjacent said converging entrance of the first exit passage, a fourth transverse bore inwardly from a side of the housing and opening into the vacuum chamber of said second venturi pump, air-inlet means communicating with the venturi inlet nozzles of both said first and second venturi pumps, a vacuum manifold connected to said housing and having a vacuum chamber communicating with each of said second, third and fourth transverse bores and having a vacuum flow inlet designed to be connected to a container to be evacuated, and independent vacuum-sensitive valve means supported between said vacuum manifold and each of said second and third transverse bores to sequentially close communication between the first and second vacuum chambers of the longitudinal bore and the chamber of the manifold when the vacuum force within the manifold increases to a value greater than the vacuum force within said first and second vacuum chambers, the chamber of the manifold being open to the fourth transverse fore and to the vacuum chamber of the second venturi pump at all times in order to develop a high vacuum force in the manifold chamber, and the chamber of the manifold being open to the second and third transverse bores only when the vacuum force within the manifold chamber is low, to provide a high vacuum flow through the manifold chamber until the vacuum force therewithin increases.