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 TM 55-1905-220-14-7
3-207. HYDRAULIC CUB PUMP UNIT - BRAKE VALVE - MAINTENANCE INSTRUCTIONS (Cont).
(6) Fluid leakage trapped between the piston and the spool escapes through the center hole of the
spool, into spring chamber D, through drain passage E to chamber B and tank, or externally to tank depending
on the position of the top cover.
(7) Operation of this valve when used with a gravity returned single acting ram is such that pump fluid
passes free flow into secondary chamber B, then through the check valve and chamber A into the ram.
Pressure buildup in the ram closes the spool.
(8) When the work stroke is completed, fluid flow is diverted from the secondary port by directing the
pump delivery to tank.
(9) On the return stroke, trapped fluid under pressure in the primary port holds the valve spool and
check valve closed until a small amount of fluid bleeding-off through the needle valve or orifice reduces the
trapped pressure.
(10) When pressure drops below the valve setting, the spring forces the valve spool to open directing the
discharge flow through the secondary port to tank.
3-3212
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