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 TM 55-1905-219-14-7
3-207. HYDRAULIC CUB PUMP UNIT - BRAKE VALVE - MAINTENANCE
INSTRUCTIONS
A
DESCRIPTION.
1. The brake valve is provided with an integral check valve which permits reverse free flow from the secondary
port to the primary port when the valve is closed.
2. The brake valve is internally drained and remotely operated. It is used primarily as an unloading valve where
the secondary port must be connected directly to the tank. Application of external pressure permits the valve to open fully
independent of the primary pressure. Type 4 valves can also be used as remotely operated counterbalance or brake
valves when provided with the integral check valve.
B.
INSTALLATION.
1. These gasket mounted valves are teed into the supply line. The tee connection is piped to the bottom, or
pressure port in the sub- plate, or to the back surface of the mounting area. The top, or secondary port is piped to the
tank or to the secondary circuit with the covers arranged for internal or external draining and direct or remote control
depending on the valve action required.
2. The point at which the valve begins to function is determined by the position of the adjusting screw (which
varies the force exerted by the spring on the spool), referred to as the pressure setting of the valve. Clockwise rotation of
the screw increases pressure. Counterclockwise rotation decreases pressure.
3. The effective areas of the spool exposed to hydraulic pressure in primary chamber A being equal, the spool
is hydraulically balanced and held in a normally closed position by the force of the spring. When pressure in primary
chamber A - which is effective on the piston through passages C - exceeds the adjusted pressure setting, the piston is
forced upward, moving the spool accordingly.
4. The spool moving upward opens secondary chamber B permitting pump delivery to flow into the secondary
circuit, while maintaining a minimum pressure in primary chamber A equal to the pressure setting of the valve.
5. When the primary pressure decreases, co pression of the spring overcomes the hydraulic force effective on
m
the piston and the spool closes blocking flow to chamber B.
3-3206
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