HYDRAULICS – CX130/CX160
5 - 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) A regeneration valve inside the main control valve provides additional speed.
3) When an anti-drift valve in the arm close circuit is opened, arm-closing movement is
achieved.
The oil flow from pump1 (front pump) enters the PR port of the control valve and the oil flow
from pump2 (rear pump) enters the PL port. When the hand control is operated for arm in
pilot pressure is directed to the cushion valve. It is then routed to the arm control spool in the
main control valve. The arm1 control spool is shifted arm-in movement is executed. Pump2 is
used for arm-in. If arm only is operated flow from pump1 is routed to the arm circuit for dual-
pump operation. (2-speed)
The pilot pressure to the arm1 control spool is sent to the arm2 control spool on the other
side of the main control valve. The control spool is shifted and sends pump1 oil flow to the
arm closing 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 an orifice in the anti-drift valve. With equal pressure on
both sides 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 control spool is shifted for arm in
(close) pilot pressure is sent through the arm control spool to the anti-drift check valve. This
opens the check valve an allows the “charged” oil in the spring chamber to exit to the return
circuit, which allow the anti-drift valve to open and arm in is activated.
Cylinder return oil must pass through a regeneration valve to the return circuit. The valve is
spring biased to the restricted position (orifice) with pilot assist from the return circuit. Pump
supply pressure is piloted to the non-spring side of the regeneration valve. As long as pump
pressure is a high enough the regeneration valve will stay shifted to the unrestricted position.
However, if the pump pressure lowers due to cavitation the valve will shift to the restricted
position, which creates backpressure in the cylinder return circuit. This oil is then available to
the supply side by way of a check valve between the two circuits.
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