Internal gear pump having a feed groove aligned with the roots of the idler teeth

An internal gear pump comprising:

• a casing comprising a pump chamber, an open end and an inlet, the pump further comprising a shaft connected to a rotor, the shaft passing through the casing, the rotor being disposed in the pump chamber,
• the rotor comprising a plurality of circumferentially disposed and spaced apart rotor teeth that extend axially towards the open end of the casing and radially inwards,
• the open end of the casing being connected to a head plate, the head plate comprising an inside surface that faces the rotor, the inside surface of the head plate comprising a crescent disposed vertically above at least a portion of the rotor teeth and that extends outwards from the head plate and towards the rotor, the crescent comprising an upper surface that defines an arc,
• the inside surface of the head plate further comprising an idler feed groove communicating with the inlet and disposed vertically above and spaced apart from the upper surface of the crescent by an ungrooved section of the head plate,
• the inside surface of the head plate being connected to an idler, the idler comprising a plurality of radially, outwardly extending idler teeth disposed between a plurality of roots, the crescent being disposed between a portion of the rotor teeth and a portion of the idler teeth, the idler feed groove being aligned with the roots of the idler teeth and only a portion of the idler teeth that extend radially outwards across the ungrooved section of the head plate and towards the upper surface of the crescent, no portion of the inlet being disposed below the crescent, each of the idler teeth being received between two of the rotor teeth,
• the idler feed groove providing communication between the inlet and the idler roots.