TM 5-3805-280-24-1
Theory of Operation
attachment plumbing. The return circuit is a low
The auxiliary hydraulic circuit is used to power the
pressure only circuit and returns directly to the return
hydraulic clamp on the model (250LCR), the rock drill
line just before it enters the reservoir. The rock drill
attachment on the model (250LCRD and the hose reel
return oil does not go through the oil cooler circuit.
on both models. The auxiliary lines use screw-together
couplers to attach the attachment hoses. The couplers
The hydraulics for the hose reel is activated by a micro
can be connected under pressure.
switch located behind the cab. Turning the micro
switch to the ON position will energize a solenoid and
The hydraulic clamp requires two-way hydraulic flow. A
allow pilot oil to flow to the check valve and then to the
foot pedal located in the cab is used to control the
flow regulator. The flow regulator is located next to the
two-way movement of the hydraulic clamp by varying
micro switch and contains a lever so that the operator
the foot pedal either up or down. The foot pedal
can control the amount of oil sent to the hose reel. At
auxiliary pilot controller is connected directly to both
the same time, oil is flowing through the pressure
ends of the auxiliary spool. The auxiliary spool controls
reducing valve to deswash the front pump so it will
the amount of and direction of pilot oil to the auxiliary
disable the main valves (Arm, Boom, Proper, and
spool, which in turn controls the oil flow and the clamp
Bucket) by not providing oil flow to them.
cylinder.
The system also controls the flow volume of oil to the
The rock drill (Type II machine) requires flow in only
rock drill, hydraulic clamp and hose reel by reducing
one direction. A switch located on the control panel
the pump regulation pressure with a pressure reducing
inside the cab activates a solenoid valve which directs
valve. This controls the stoke of the pump to provide
pilot pressure to the top of the main auxiliary spool.
only the amount of oil needed by the attachments.
This shifts the spool to direct pressure oil to the
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