PUMPS
SUB-SECTION 4B
outlet section is approached, the chamber volume decreases
PRINCIPLES OF OPERATION
and the fluid is forced out onto the system.
Fluid enters the pumping cartridge through the inlet port
and is discharged through the pressure plates to the outlet
The intra-vane design provides a means of controlling the
ports. The action of the pumping cartridge is illustrated in
outward thrust of the vane against the cam ring to maintain
Figure 4B-2.
the tip loads within reasonable limits. In the intra-vane car-
tridge, full system pressure is continuously applied for out-
The rotor is driven within the cam ring by the driveshaft,
ward vane thrust only over the area between the vane and
which is coupled to the pump drive. As the rotor turns,
insert. This area is small and thrust is correspondingly light.
centrifugal force on the vanes, aided by under-vane pressure
During vane travel through pressure areas, full system pres-
fed from the outlet port, causes them to follow the ellip-
sure is also applied against the bottom of the vane. The
tical inner surface of the cam ring.
valving of pressure to and from the bottom area of the vane
is through holes drilled in the rotor, as shown in Figure
Radial movement of the vanes and turning of the rotor
4B-3. This selective application of pressure maintains the
cause the chamber volume between the vanes to increase as
vane in constant radial hydraulic balance in all positions.
the vanes pass the inlet section of the cam ring. This results
in a low pressure condition which allows atmospheric pres-
The cam ring is shaped so that the two pumping chambers
sure to force fluid into the chambers.
are formed 180 degrees apart (see Figure 4B-2). Thus,
opposing hydraulic forces which would impose side loads
This fluid is trapped between the vanes and carried past a
on the driveshaft cancel each other out.
sealing land to the outlet section of the cam ring. As the
Figure 4B-2. Pump Cartridge Operation
4B-2
