Vacuum pressure selection and generation device

In an aspirator vacuum pressure generating assembly having a housing provided with a first vacuum port connected to a source of variable vacuum pressure, a second vacuum port connected to a device requiring a predetermined minimum level of vacuum pressure, and an inlet port connected to receive positive air pressure, the improvement comprising:

• a venturi aspirator connected to receive positive air pressure through said inlet port and to operatively and selectively discharge air through said first vacuum port and to selectively generate vacuum pressure in said second vacuum port at at least said predetermined minimum level of vacuum pressure;
• valve means operatively responsive to the vacuum pressure in said first vacuum port to selectively permit the flow of positive air pressure through said venturi aspirator so that vacuum pressure is operatively generated by said aspirator in said second vacuum port only when the vacuum level in said first vacuum port is less than said predetermined minimum vacuum level;
• and check valves operatively acting between and responsive to pressures in said first and second vacuum ports and also between and responsive to pressures in said second vacuum port and venturi aspirator to establish a vacuum pressure connection between said second vacuum port and only the greater of the vacuum pressures in said first vacuum port and that generated by said venturi aspirator.

A subatmospheric pressure selection and generation assembly comprising:

• a housing defining first and second and third chambers,
• a first port opening into said first chamber and adapted to be connected to a device utilizing subatmospheric air pressure when operating;
• a second port opening into said second chamber and adapted to be connected to a source of varying subatmospheric air pressure;
• a third port adapted to be connected to a source of superatmospheric air pressure, said third port having a venturi therein, said venturi being in said third chamber and having an opening connecting the throat of said venturi with said third chamber so that the flow of air at superatmospheric pressure through said third port aspirates air from said third chamber through said opening to generate a subatmospheric air pressure in said third chamber, said third port including a passage extending beyond said venturi and opening into said second chamber through a valve seat;
• first passage means communicating said first and second chambers and having first check valve means opening to permit air flow only from said first chamber to said second chamber through said first passage means;
• second passage means communicating said second chamber and said second port and having second check valve means opening to permit air flow only from said second chamber to said second port through said second passage means;
• third passage means communicating said first chamber and said third chamber and having third check valve means opening to permit air flow only from said first chamber to said third chamber;
• and shut-off valve means including a flexible wall forming one wall of said second chamber, a valve mounted on said flexible wall and positioned to open and close said third port at said valve seat upon movement of said flexible wall, and spring means operatively acting on said valve to continually urge said valve away from said valve seat, said flexible wall having one side exposed to atmospheric pressure and the other side exposed to pressure in said second chamber;
• the subatmospheric air pressure in said second chamber acting on said flexible wall to keep said third port closed at said valve seat when the valve of the subatmospheric air pressure in said first and second ports and chambers is sufficient for operating the device, said third check valve means being closed and said first and second check valve means being open to supply subatmospheric air pressure from said second port to said first port through said second and first chambers and said second and first passage means;
• said spring means acting on said flexible wall and valve to open said third port at said valve seat when the value of the subatmospheric air pressure in said second port and chamber is insufficient for the device, said subatmospheric air pressure flowing through said venturi to induce a sufficient subatmospheric air pressure for the device in said third chamber, the differential air pressure acting to open said third check valve means and close said first check valve means so that the device will receive the subatmospheric air pressure of said third chamber and not the insufficient subatmospheric air pressure of said second chamber.