(57) A gerotor or N(N+1) type pump comprises outer and inner lobed rotors 10, 11 defining
pumping chambers 16 and has an inlet port 18 and two outlet ports 19, 20. Ports 19,
20 are separated from each other by a radially extending land 22. Between each pair
of neighbouring lobes on the inner rotor 11 a radial slot 24 is formed which opens
to the periphery of the rotor and extends inward a sufficient distance to overlap
the two outlet ports 19, 20 radially when the said two lobes flank circumferentially
opposite sides of the land 22. The circumferential extent of each slot 24 is sufficient
to ensure that there is always a leakage path from the pumping chamber to which the
slot opens to one or other of the two outlet ports as the slot passes the land 22.
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