Operator`s manual

The relief valve of the outrigger control valve (50) limits the outrigger operating pressure to 1000 psi.
To prevent ladder operation before the outriggers are deployed, micro switches (see Figure 6-7, number
150) at the outrigger control the current to the ladder control console. When the outriggers are deployed,
the outrigger micro switches close causing the solenoid-operated switches (see Figure 6-7, number 154)
to close allowing current flow to the ladder control console via a contact ring (see Figure 6-7, number 10).
5.5 LADDER HYDRAULICS
Selector valve (12) directs the flow of oil to the ladder circuit through the main oil joint (13) at the
Turntable, when the "In-Ladder" position has been selected. The Relief/Unloader Valve allows the unused
oil to return to the reservoir (1).
In the compartment under the Ladder Control Console there are three Proportional Valves incorporated in
a monoblock design (16). The valves are part of the ladder hydraulic circuits controlling elevation,
depression, rotation, extension and retraction. Each Proportional Valve consists of a pressure
compensated flow control valve, a solenoid-actuated, four-way, three position, spring-centered directional
control valve, and a pressure relief valve. Refer to Section 8 for adjustments to the Proportional Valves.
The Relief/Unloader Valve (14), which is on the Ladder Turntable (see Figure 8-1), is also adjustable.
Refer to Section 8 for adjustments to this valve.
Elevating and Lowering the Ladder - to elevate the ladder, the directional control valve in the Proportional
Valve (16) is operated by a solenoid and oil passes through the pressure compensated flow valve which
controls the amount of hydraulic fluid the directional control valve receives by controlling the rate of flow.
The relief valve in the Proportional Valve is set at about 1550 psi and protects the ladder from an overload
caused by striking an object when raising or lowering the ladder.
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