Lift coard concealable venetian blind lift control mechanism

A lift cord concealable Venetian blind lift control mechanism installed in a Venetian blind, which comprises a top rail, a bottom rail, a plurality of slats arranged in parallel between said top rail and said bottom rail, and two lift cords vertically inserted through said slats and arranged in parallel, the lift cord concealable Venetian blind lift control mechanism comprising:

• a base installed in one of the top and bottom rails of said Venetian blind, said base comprising two screw rods axially horizontally aligned in a line between said lift cords, an axle hole axially extended through said screw rods;
• a revolving rod inserted through said axle hole of said base for free rotation relative to said base, said revolving rod having two distal ends respectively extended out of said screw rods;
• a spring member mounted in said base and adapted to impart a torsional force to said revolving rod;
• and
• two bobbins respectively threaded onto said screw rods and coupled to the ends of said revolving rod for synchronous rotation with said revolving rod and for axial movement relative to said screw rods to wind up/let off said lift cords upon forward/backward rotation of said revolving rod.