Alamo MACHETE Product Service Manual page 90

MOTOR - PUMP DIS-ENGAGE
Motor Circuit Disengage (w/ Engine Running)
The Alamo Closed Loop Motor Circuit is considered to be Neutral when there is no output being
generated by the Variable Displacement Pump, as the Shaft, Internal components and Charge
Pump are being driven by Tractor Engine. The Camplate is in the centered position and the
length of Stroke of the Pistons is equal, therefore there is no flow being generated by the pump
At this point the Charge Pump is drawing Oil through a Suction Screen from the Tank
to provide flow to perform the following functions.
1. Keep the Circuit Primed and make up internal leakage.
2. Maintain Back Pressure on Pump and Motor Pistons
3. Operate Control Functions to Start Pump.
4. Maintain Temperature Control, to prevent Oil Heating in Pump.
Oil from the Charge Pump is directed to two dual purpose system Relief and Check
Valves (Figure 41). Since the Charge Pressure is greater than the pressure in either side of the
Closed Loop, The Check Valves open and charged Oil (at Charge Pressure) is available to both
sides of the closed Loop. When the System is primed, any excess Oil is relieved through the
Charge Pump relief Valve, which maintains a pressure of 250 to 300 PSI.
The Piston Pump remains in Neutral as long as the Campmate remains in the centered
position, this is controlled by the Servo Control System, If Pump does not stay in neutral check
the Neutral Adjusting screw. This is usually noticed by Motor wanting to run.
Neutral
Centering
Spring
Solenoid
Servo
Control
Servo Piston
Machete (Service Manual) 04/04
© 2004 Alamo Group Inc.
Port "D"
To Motor
Camplate
Piston Asy.
Case Drain
Neutral Adjustment
Servo Control Supply Oil
System Relief &
Check Valve
System Relief
& Check Valve
FIGURE 41 PUMP
90
Port "C"
From Motor
Gerotor
Charge
Pump
Charge
Pump
Suction
Charge
Pump
Relief
Valve