The pump discharge pressure generates a force on the pump cover, which is constructed from an outer ring and an inner, spring-loaded plate. As long as the spring force is larger than the pressure force, the inner plate maintains its position and seals suction and discharge side. If the pressure force exceeds the spring force, the inner plate moves axially and the developing clearance between rotor and inner plate enables slip from the suction to the discharge side. The rotor / inner plate
clearance closes with decreasing discharge pressure.
An elastic diaphragm seal between inner plate and outer ring encapsulates all other parts of the VARIOCAP from the pumped fluid.