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 TM 55-1905-220-14-7
3-206. HYDRAULIC CUB PUMP UNIT - HYDRAULIC PUMP - MAINTENANCE INSTRUCTIONS
A.
GENERAL.
(1) This pump is used to develop hydraulic fluid flow for the operation of the steering system equipment.
The positive displacement pumping cartridges are the rotary vane type with shaft side loads hydraulically
balanced.
(2) All units are designed so that the direction of rotation, pumping capacity and port positions can be
readily changed to suit particular applications.
B.
ASSEMBLY AND CONSTRUCTION.
(1) The unit consists principally of a ported body, a ported cover and a pumping cartridge. Components
of the pumping cartridge are an elliptical cam ring, a slotted rotor splined to fit the drive shaft and twelve vanes
fitted to the rotor slots.
(2) The pumping cartridge cam ring is sandwiched between the body and cover. A ball bearing and
bushing located in the body and pressure plate respectively support each end of the drive shaft and center the
rotor within the cam ring. As the drive shaft is driven by the prime mover, the rotor and vanes generate flow by
carrying fluid around the elliptical cam ring contour. Fluid enters the cartridge through the inlet port in the body
and is discharged through the pressure plate into the outlet port of the cover.
(3) Fluid flow is developed by the pumping cartridge. The action of the cartridge is illustrated below.
The rotor is driven within the cam ring by the driveshaft, which is coupled to a power source. As the rotor turns,
centrifugal force causes the vanes to follow the elliptical inner surface of the cam ring.
(4) Radial movement of the vanes and turning of the rotor cause the chamber volume between the
vanes to increase as the vanes pass the inlet sections of the cam ring. This results in a low pressure condition
which allows atmospheric pressure to force fluid into the chambers. (Fluid outside the inlet is at atmospheric
pressure or higher).
(5) This fluid is trapped between the vanes and carried past the large diameter or dwell section of the
cam ring. As the outlet section is approached, the cam ring diameter decreases and the fluid is forced out into
the system. System pressure is fed under the vanes, assuring their sealing contact against the cam ring during
normal operation.
3-3199
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