Patent ID: 7464416

Claim:
A passive buoyancy mechanism for maintaining a correlation between length of a buoyant pool cover and revolutions of a cover drum completely submerged in a pool bottom trough around which the pool cover spirally winds and unwinds in a retraction-extension cycle comprising, in combination: a) a buoyant cylinder completely submerged, buoyed within winding side quadrants of the pool bottom trough adjacent and parallel to the cover drum; b) strapping fastened between the submerged buoyant cylinder and an upper, unwinding side of the pool bottom trough, tensioned by buoyant forces created by the submerged buoyant cylinder, stretching down winding side quadrants of the trough, around and underneath the spirally wound up cover, and up unwinding side quadrants of the pool bottom trough frictionally engaging exterior surfaces of the spirally wound up layers of the cover as the cover spirally winds-up and unwinds from around the cover drum for resisting radial expansion of the submerged, spirally wound layers of the buoyant wound up around the cover drum; c) means for rotating the cover drum a specified number of revolutions in a winding direction for spirally winding the cover around the cover drum retracting the pool cover from an extended position covering a pool surface to a storage position completely submerged, spirally wound up around the cover drum in the pool bottom trough; d) means for preventing cover drum rotation when the pool cover is spirally wound up to the storage position; and e) means for rotating the cover drum the specified number of revolutions in an unwinding direction for spirally unwinding the buoyant cover from around the cover drum extending the pool cover from the submerged, storage position to the extended position covering the pool surface.