Variable flow impeller-type water pump with movable shroud

A variable capacity coolant pump comprising:

• a pump housing for providing passage of coolant;
• a rotatable shaft extending axially through said housing;
• an impeller coupled to said shaft and having a flange extending radially outwardly from said shaft and a plurality of vanes projecting axially from said flange and configured to cause flow of the coolant through said housing;
• a shroud operatively coupled to said shaft for axial movement therealong relative to said impeller between an extended position whereby the entire surface of said vanes are surrounded and covered by the shroud and a retracted position whereby only a portion of the vanes are surrounded and covered by the shroud for varying the amount of coolant flow through said housing by said impeller, said shroud including a cup-shaped body having a plurality of grooves therethrough for axially receiving said corresponding plurality of vanes during movement between said extended and retracted positions for variably surrounding and covering the surfaces of said vanes exposed to the coolant;
• a sleeve rotatably journaled to said impeller and axially coupled to said shroud for guiding said shroud between said extended retracted positions in response to a change in angular position of the shroud and impeller relative to the shaft;
• and
• an actuator operatively coupled to said shroud for automatically controlling said axial movement of said shroud between said extended and retracted position for selectively controlling the amount of coolant flow through said housing by said impeller.