Lumber support system for a vehicle seat

A lumbar support system for a vehicle seat, comprising:

• a pressurized air supply source;
• an air bag disposed at a position corresponding to the waist of a person seated in the vehicle seat and between the upholstery sheet of the vehicle seat and the cushion material supporting the upholstery sheet;
• a valve casing being attached to said vehicle seat and including a partition wall partitioning the interior of said valve casing into a first chamber and a second chamber, an inlet port opening into said first chamber and connected to said pressurized air supply source, a discharge port opening into said first chamber and allowing the communication of said first chamber with the exterior of said valve casing, an outlet port opening into said second chamber and allowing the communication of said second chamber with said air bag, and an opening formed in said partition wall for communicating said first chamber with said second chamber;
• a manually-operable push button movably supported on said valve casing and having push rod fixed thereto at one end of said push rod;
• a first normally closed valve formed within said first chamber for normally interrupting the communication between said first chamber and said discharge port, said first normally closed valve including a first valve member fixed to the other end of said push rod of said push button and adapted to close a release passage communicating said first chamber with said discharge port by a spring force, said first normally closed valve being adapted to open said release passage when said push button is manually operated;
• and
• a second normally closed valve formed within said second chamber for normally interrupting the communication between said first and second chambers, said second normally closed valve including a valve rod extending through said opening formed in said partition wall and being slidable coaxially with said push rod, said second valve further including a second valve member fixed to one end of said valve rod and projecting into said second chamber, said second valve member adapted to normally close said opening by a spring force, said second normally closed valve being constructed and adapted so as to open said opening against said spring force due to the movement of said first valve member of said first normally closed valve for discharging pressurized air prevailing in said air bag to the exterior of said valve casing via said first and second chambers, said release passage and said discharge port after said first normally closed valve opens said release passage through the manual operation of said push button,
• whereby an inadvertent opening of only said first valve by said push button does not release air pressure in said air bag.