HYDRAULICS – CX210/CX240
6 - 30
CX EXCAVATORS
ATTACHMENT
Arm Close (In)
1) Two pump flows inside the control valve are combined, when the arm1 and arm2 control
spools are shifted.
2) When a built-in anti-drift valve in the control valve is opened and the arm1 spool is
shifted, arm closing is achieved.
3) A regeneration valve provides additional speed.
The oil from pump1 (front pump) enters the P1 port of the control valve and the oil from
pump2 (rear pump) enters the P2 port. When the hand control for arm in is operated, pilot
pressure is directed through the cushion valve to the arm1 control spool in the main control
valve. The arm1 control spool is shifted and arm-in is executed. When the arm1 control spool
is shifted pilot pressure is routed to the anti-drift pilot valve and shifts the valve. This allows
the trapped oil in the spring chamber of the anti-drift valve to escape to tank. Which allows
the valve to open for arm-in operation. Pump1 is used for the arm circuit. If arm only is
operated flow from pump2 is routed to the arm circuit for dual-pump operation (2-speed).
The pilot pressure sent from the arm-in control is also sent to the arm2 spool on the pump2
side of the main control valve. The spool is shifted and diverts pump2 oil to the arm-in
cylinder circuit at the arm1 control spool.
When the arm is opened (out) the spring chamber of the anti-drift valve is “charged” with arm
out pressure. This is done through a pilot signal from the cylinder circuit, which passes
through the anti-drift pilot valve to the spring chamber of the anti-drift valve. With equal
pressure on each side of the valve the spring is able to hold the valve closed. This keeps arm
drift through the control spool at a minimum. When the arm is closed (in) a pilot signal from
the arm control pilot circuit is also routed to the anti-drift pilot valve. The valve is shifted and
allows the “charged” oil in the spring chamber to exit to the return circuit. Now the anti-drift
valve will open and arm close (in) is activated.
The cylinder return oil is routed through a regeneration valve. This is a two-stage restricted
valve, which creates backpressure in the return circuit. Pump pressure will normally keep the
regeneration valve in the least restrictive position. The valve is spring biased to the most
restricted position plus a pilot signal from the return circuit. If the pump pressure should be
reduced, because supply cannot keep up with demand the regeneration valve will shift to the
most restricted position. This will force return oil to the supply circuit across a check valve
inside the arm1 control spool.
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