Service Manual

HYDRAULIC COMPONENTS (cont’d)
Check Valve - A check valve can be used for
pressure control or directional control. It usually
consists of a ball and seat area.
A spring may
be used to hold the ball on the seat.
Some check valves are adjustable. This is
accomplished by using a spring with a different
rate, shimming the existing spring or
compressing the spring with a threaded adjuster.
Push
Valve - A push valve is a flow control
valve used to open a pump/motor circuit.
Manually opening the circuit allows oil to bypass
from one side
of the circuit to the other or allows
oil to escape back to the reservoir.
The push valve allows the unit to be moved
without starting the engine. Most, but not all
hydrostatic transmissions use a push valve.
I I I
3.4297.4111
3.4297.412
Relief Valve - A relief valve is a pressure
control valve which is used to protect a hydraulic
circuit from pressures which are higher than the
circuit’s design.
13
3.4297.413
Productivity Series