Internal gear pump with improved communication between inlet and idler and between inlet and rotor

An internal gear pump comprising:

• a casing comprising an inlet, an outlet, an open outboard end and an inboard end through which a rotor shaft passes, the open outboard end enclosed by a head, the head and casing defining a pump chamber, the pump chamber has a central axis, the rotor shaft connected to a rotor disposed in the pump chamber,
• the head including an inner surface that faces the pump chamber, the inner surface connected to a boss extending from the inner surface into the pump chamber,
• the boss comprising an idler support connected to a crescent support, the idler support rotatably connected to an idler, the idler rotates about an idler axis,
• the crescent support partially covered by and connected to a crescent that extends away from the head and that is disposed below the idler, the crescent support further comprising a liquid directing step that extends from the crescent and towards the inlet,
• the rotor comprising a plurality of circumferentially disposed rotor teeth extending radially inwards towards the central axis, the idler comprising a plurality of idler teeth extending radially outwards away from the idler axis,
• the boss comprising a lower wall disposed below the crescent support and that extends from the crescent support downward to the casing, the boss, casing and inner surface of the head defining a rotor feed slot between the liquid directing step and the casing and extending from the lower wall towards the inlet for providing communication between the inlet and the rotor teeth.

A method for pumping liquid at a high speed, the method comprising:

• providing an internal gear pump comprising a casing comprising an inlet, an outlet, an open outboard end and an inboard end through which a rotor shaft passes, the open outboard end enclosed by a head, the head and casing defining a pump chamber, the pump chamber has a central axis, the rotor shaft connected to a rotor disposed in the pump chamber, the head including an inner surface that faces the pump chamber, the inner surface connected to a boss extending from the inner surface into the pump chamber, the boss comprising an idler support connected to a crescent support by a middle wall, the idler support rotatably connected to an idler that rotates about an idler axis, the boss and head defining an idler feed slot between the liquid directing step and the idler support and extending from the middle wall towards the inlet, the crescent support partially covered by and connected to a crescent that extends away from the head and that is disposed below the idler, the crescent support further comprising a liquid directing step that extends from the crescent and towards the inlet, the rotor comprising a plurality of circumferentially disposed rotor teeth extending radially inwards towards the central axis, the idler comprising a plurality of idler teeth extending radially outwards away from the idler axis and disposed radially within the rotor teeth, the boss comprising a lower wall disposed below the crescent support and that extends from the crescent support downward to the casing, the boss, casing and inner surface of the head defining a rotor feed slot between the liquid directing step and the casing and extending from the lower wall towards the inlet;
• rotating the rotor shaft and rotor;
• directing fluid from the inlet and through the idler feed slot to the idler teeth;
• and
• directing fluid from the inlet and through the rotor feed slot to the rotor teeth.