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TM 55-1905-223-24-9
(3) Vane Pump. The pump shaft and motor shaft are aligned and mechanically coupled. At the heart of this
pump is a slotted rotor into which 12 sliding vanes are fitted. Because these precision vanes are replaceable drop-in
elements, repair and overhaul are simplified.
d. Uniblock 2A Manifold (FIGURE 1-12). System I and system 2 have identical uniblock 2A manifolds.  I Input to
each manifold is piped directly from outlet of the associated vane pump into the manifold inlet through an inlet filter. The
manifold inlet provides two internal flow paths: path (a) flows into the pump port of the solenoid-operated four-way
directional valve, and path (b) flows into the inlet port of the vent/relief cartridge. With no voltage on the solenoid valve,
flow path (a) is closed. In this configuration, the vent/relief cartridge vents the low pressure flow back into the reservoir.
Once the solenoid is energized, however, path (a) opens, causing path (b) to close. These actions couple the pump
discharge directly to both actuating cylinders. In this configuration, system pressure builds up until the rudders respond.
This pressure will not exceed the 930 psi setting of the manifold relief valve. In addition to the manifold body, each
uniblock assembly incorporates the following components: directional valve, shuttle valve, lockvalve, and two outlet
filters. Descriptions of the manifold components follow.
(1) Manifold Inlet Filter. This filter is a cleanable 60-wire mesh screen that traps particles over .010 inch in
(2) Solenoid-Operated Four-Way Directional Control Valve (FIGURE 1-12).  This valve accepts 24 Vdc
electrical rudder orders and initiates right or left rudder travel. The valve is made up of a central body with identical right
and left operating solenoids. Lateral motion of the armature in either solenoid repositions the valve spool, changing the
interconnections between inlet and outlet ports. Port P is the valve inlet from the vane pump. Port T is the valve outlet
to the reservoir. Ports A and B are inlets or outlets, depending on the position of the sliding spool. Outflow from port A
drives the piston in one direction, causing the displaced fluid on the other side of the piston to return to the reservoir via
port B. When neither solenoid is energized, internal springs position the spool in the center. In this position, port P is
blocked. This causes the pump discharge to open the vent/relief cartridge between the pump and the directional valve.
The discharge returns to the reservoir. In the center position, ports A and B are internally connected to port T (and to the
(3) Vent/Relief Cartridge. This assembly has three fluid ports: an inlet port, a vent/relief outlet port, and a
pilot inlet port. When no pressure is sensed at the pilot inlet port, fluid enters the inlet port and flows out the vent/relief
outlet port to the fluid reservoir. When the pilot inlet port is pressurized, flow between the inlet and outlet ports is cut off.
Cutoff pressure is applied to the vent/relief cartridge via the shuttle valve as described below.
(4) Shuttle Valve (FIGURE 1 -12). The shuttle valve intercepts the flow of fluid out of ports A and B of I the
solenoid valve so that when either solenoid is energized, a pilot inlet flow path to the vent/relief cartridge closes off the
return of fluid to the reservoir via this cartridge. Outflow from the shuttle valve also enters the 930 psi relief valve, so
that pressures exceeding 930 psi are vented back to the reservoir.
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