US Patent 7726520 Metered dispenser with feed-containing piston drive mechanism

A metered dispenser includes a housing including a reciprocable piston drive stem including an inlet opening at a first end thereof, a floating piston at a second end, and a passage between the first and second ends. An inlet valve is provided adjacent the first end for permitting entry of liquid product into the passage. A biased cocking mechanism is reciprocally disposed substantially within the housing. A biased loading mechanism is movable in a second generally opposite direction by the cocking mechanism, and is engageable with the piston drive stem to move the drive stem in the second direction. When the cocking mechanism is moved from an initial rest position toward the second direction, a series of operations allow the loading mechanism to project the drive stem in the first direction to dispense a metered dose of liquid product through a discharge orifice provided adjacent the second end.