SUB-SECTION 4B
PUMPS
Figure 4B-38. Pressure Feed to Vanes
The intra-vane design provides a means of controlling the
2. Disconnect the suction and outlet lines from the pump.
outward thrust of the vane against the cam ring to maintain
Cap the lines and plug the pump ports to prevent the entry
the tip loads within reasonable limits. In the intra-vane car-
of foreign material into the pump or hydraulic system.
tridge, full system pressure is continuously applied for out-
3. Block the pump in position against the pump drive so
ward vane thrust only over the area between the vane and
that it will not drop when the capscrews are removed.
insert. This area is smell and thrust is correspondingly light.
Remove the two capscrews securing the pump to the pump
During vane travel through pressure areas, full system pres-
drive. Slide the pump beck from the pump drive until the
sure is also applied against the bottom of the vane. The
drivesheft is clear of the pump drive, and remove the pump
valving of pressure to and from the bottom area of the vane
to a suitable repair area.
is through holes drilled in the rotor, as shown in Figure
4B-38. This selective application of pressure maintains the
vane in constant radial hydraulic balance in all positions.
The cam ring is shaped so that the two pumping chambers
are formed 180 degrees apart (see Figure 4B-27). Thus,
opposing hydraulic forces which would impose side loads
on the driveshaft cancel each other out.
The pressure plate seals the pump chamber as shown in
Figure 4B-39. System pressure is effective against the area
at the back of the plate, which is larger then the area ex-
posed to the pumping cartridge. Thus, an unbalanced force
holds the plate against the cartridge, sealing the cartridge
and providing the proper running clearance for the rotor
and vanes. The pressure plate also contains passages for
feeding pressure to the space between the vanes and inserts.
REMOVAL
To remove a pump from the pump drive, proceed as fol-
lows:
Figure 4B-39. Pressure Plate Operation
1. Turn the suction line valve to the closed position.
4B-23
