Circular rotor 1 rotates about fixed axis A and has diametral slot a in which vane 2 slides. The internal surface of housing 3 has the shape of a cardioid with its pole at point A. When rotor 1 rotates, vane 2 slides with its ends along the internal surface of housing 3, delivering liquid in the direction of the arrows.
$3810$LHP,RP$