A hands-free breast pump that includes a balanced push-pull reciprocating drivesystem that applies pumping force to a vacuum chamber formed by a breast interfacecup during inward and outward pump strokes. The breast pump includes a breastcup that has a resilient bellows structure that partially collapses the volumeof the vacuum chamber during the inward stroke and recovers the volume of the vacuumchamber during the outward stroke. The pump mechanism includes a cam drive systemthat translates rotary electric motor power into reciprocating linear actionof an actuator arm that drives the bellows structure. The bellows structure actslike a spring that charges (resists the pump force) during the inward stroke anddischarges (assists the pump force) during the outward stroke, and the shapeof the cam track is designed to produce a desired operating profile for the pump.
