Figure 20-5. Rotary Pumps.
As the two rotors turn, the openings between them are
wedging action of the oil as it is forced toward the outlet
filled with oil. This oil then is forced out from between the
port by the vane.
rotors as the inner-rotor lobes enter the openings in the
outer lobes. This action is much like that in the gear-type
Internal-External Gear Type. The internal-
external gear pump is composed of a large internal gear,
driven by an external gear offset from center. The space
20-6. Vane Type. The oil pump shown in figure 20-6 is a
between the two gears is occupied by a filler block (fig.
vane type. An integral steel rotor and shaft, one end
20-7). As the small gear rotates, it meshes with, and
supported in the pump flange and the other end in the
drives, the larger gear. As the gears disengage and
cover, revolves in the body, the bore of which is eccentric
come in contact with the filler block, a differential in
to the rotor. Two sliding vanes are placed 180 degrees
pressure is developed, causing oil to enter the pump. It
apart in slots in the rotor and are pressed against the
then is transported past the filler block in the teeth of both
body bore by springs in the slots. When the shaft is
gears. Because the gear teeth begin to mesh again and
rotated, the vanes pick up oil at the inlet port and carry it
more oil is carried by the gears, pressure rises in the
around the body to the outlet side, where the oil is
outlet chamber and exits through the outlet port.
discharged. Pressure is produced by the