HYDRAULICS – CX210/CX240
6 - 32
CX EXCAVATORS
FEATURES
Cushion Operation (ON) (Boom and Arm)
1) As a control spool returns to neutral (center) position, the pilot oil must return through
an orifice in the cushion valve.
2) The slow movement of the spool provides the cushion feature.
3) Cushion control only occurs in the boom and arm circuits.
During arm or boom operation, when the control lever is returned to neutral, a cushion valve
reduces the shock to the machine by preventing sudden stopping of the arm or boom
movement. The heat circuit of the cushion valve serves to improve operation during cold
weather operation.
Cushion valve operation is explained using the boom up operation as an example. When the
boom up control lever is returned to neutral, a restriction in the cushion valve creates an
imbalance between the pressure that shifted the boom1 control spool, (connected to the H
port of the cushion valve) and the neutral signal (tank) pressure at the E port. The cushion
valve shifts to a more restrictive passage and the pressure change is slowed as it is lowered
to neutral signal (tank) pressure. As the pressure lowers, the boom1 control spool returns too
neutral. By slowing the shifting of the control spool, shock to the machine is reduced.
The heat circuit of the cushion valve is part of the hydraulic return oil that flows through a
0.12-inch orifice and an in line filter before it enters the R port of the valve. The orifice raises
the oil temperature, and as the heated oil passes through the cushion valve, the temperature
of the cushion valve is raised. The increased temperature improves the operation of the
cushion valve in cold weather.
Cushion Valve
Back of cab
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