Alamo MACHETE Product Service Manual page 17

CONTROL VALVE - OPERATION
HYDRAULIC FUNCTIONS:
The Hydraulic Functions of the Machete Boom Mower are controlled by a Pilot operated
Electrically Actuated Control Valve.
GENERAL OPERATION:
This Section addresses the method of operation of the electrical part of controls. The function
of the Hydraulic Valve itself will be covered in another Section. Three Functions, The Lift, The
Dipper and the Swing are "Proportional" meaning that the Speed of operation can be slowed
down or Sped up according to the position of the Joystick Control. The Door and Tilt Functions
are "On" or "Off" only, Meaning that their speed of operation is dependent upon the volume
of Oil Flowing through the Circuit and cannot be controlled by the Joystick position. In Our
application the Oil Volume varies with the Tractor Engine Speed.
SPECIFIC OPERATION: (Figure 2)
The Electrical Power to operate the Circuits is obtained from a Switched and Fused Tractor
Voltage Source. This means that the Electrical Power Wire to the Joystick Controller should
only be connected to a Wire that has Voltage when the ignition is in the "On" Position. If
Connection of the Joystick Controller is to a constant current source it will cause power drain
on Battery and eventually Battery Failure. Furthermore the Master Switch on the Joystick
Console (Figure 5) must be in the "On" position to allow for the operation of any of the Control
Functions. To achieve Electrical Proportional Actuation, The main Spool Position is adjusted
so that it corresponds to an Electrical signal sent from the Joystick Controller. The Position
of the Joystick is Electrically sensed by a Coil and Magnet located in the Joystick Assembly
which sends the positioning information to the electric controller in the Valve. The Signal from
the Joystick is converted by the electronic Controller into Hydraulic Pressure by activating a
series of Hydraulic Valves. These Valves direct the Standby or Pilot Pressure Oil to the proper
end of the Spool to cause it to move. Likewise the position of the Spool is converted in the Spool
position transducer to feedback signal. This Signal is registered by the electronic controller
which will activate the series of valves as needed to move the spool in either direction until the
spool is positioned in accordance with the location of the Joystick. An equilibrium between the
Joystick and feedback signal is the end result.
Electric
Controller
Spool Positioning Valves
MACHETE (Service Manual) 04/04
© 2004 Alamo Group Inc.
Electric Signal for Joystick Controller
Pilot Pressure
B A
Spool Position Transducer
17
Control Valve
Segment
Handle is shown
for Illustration
FIGURE 2
Only