An electric motor drives a gearbox. A cam fitted on the
outlet gear drives a lever which lifts the hollow piston and
simultaneously compresses a spring. When the piston
reaches the top of its stroke, the lever is freed from the
cam and the piston begins its downward (working) stroke,
driven by the spring. Lubricant is sucked into the chamber
formed above the piston during its downward ejection
stroke, thus preparing the piston for the next cycle.