Theory of Operation
balance spring pushes the spool down. As the spool is
One pilot controller is used to control the propel
pushed down the passage from the control valve pilot
functions. The controller contains four valve
cap to the hydraulic oil tank (I) is closed and then is
assemblies, one for each direction of travel for each
opened to the pilot oil from pilot shutoff valve. When
the pilot oil pressure to the control valve pilot cap is
equal to the force applied by the balance spring the
The pilot controller consists of the cam and pedal (E),
spool moves up trapping the oil to the pilot cap.
plunger (D), sleeve (F), spring guide (C), spool (A),
balance spring (G), and return spring (H).
When the pedal and cam is moved to full stroke, the
plunger is pushed down further by the balance spring
In neutral, the spool is pushed up by the return spring
opening the passage through the spool more to the
to block pilot oil from the pilot shutoff valve (J). With
pilot oil. When pressure to the control valve pilot cap is
the spool up, the passage to the control valve pilot cap
equal to the force applied by the balance spring, the
(K) is connected to the hydraulic oil tank (I) by the
spool moves up until it contacts the plunger. The
passage through the spool (A).
plunger holds the spool down so the passage through
spool remains open to pilot oil. Oil pressure to the
When the pedal is pushed to move the machine, the
control valve pilot cap now equals pilot oil pressure.
cam (E) pushes the plunger and spring guide down
against the return spring and balance spring. The