Alamo MACHETE Product Service Manual page 91

MOTOR - PUMP ENGAGE
Motor Circuit Engaged (w/ Engine Running)
When the Switch and Solenoid are activated, The Servo control System moves the Camplate
to its Maximum Angle. As the Piston Block rotates, The Angle of the Camplate causes the Pistons to
move in and out of their Bores as they follow the Camplate, This results in Oil being drawn into the Piston
Bore as the Piston is pulled outward. The Oil being expelled into the other side of the Loop as the Piston
is forced back into its bore, This creates the flow of Oil necessary to power the Motor. Movement of the
Camplate angle from the neutral to maximum is set at approximately 6 seconds and is controlled by the
size of the Orifice between the Control valve & Pump Case.
Oil under charge pressure is available at the Check Seats of the combination System Relief
& Check Valves. As the Piston is drawn outwards in its bore, The combination of lower pressure in the
Piston Bore and charge pressure in Port "C" causes the Check Valve for Port "C" to come off its seat,
Allowing Oil At Charge pressure to fill the Piston Bore. As the Piston Block rotates the Oil is trapped in
its bore by the Valve Plate. As the Piston Block rotates more, the piston is forced back into its bore
expelling the Oil into Port "D" through an opening in the Valve Plate. The Higher pressure in Port "D" seats
the Check Valve for Port "D", Separating Oil in Port "C" from Oil in Port "D". Oil is forced to go through
the Motor causing Motor Rotation.
Any Leakage from the Piston Block Valve Plate, Pistons, or excess Oil from the Charge
Pump Relief Valve is vented to the case and is returned to Tank through the case Drain Port.
Neutral
Centering
Solenoid Spring
Servo
Control
Servo Piston
Relief Valve Operation:
When the pressure in Port "D" exceeds the setting of the Relief Valve (4500 PSI), the large Spring
in the Relief Valve is compressed, Opening an Orifice allowing excess Oil to relieve into the Charge
Circuit, Since the Check Valve for Port "C" is open, The Oil is available to the intake side of Pump
There is also a relief Valve in the High Pressure side of the Loop at the Motor. This Valve is set to
relieve at 4000 PSI and is in the circuit to absorb spike pressure encountered during severe operation.
Machete (Service Manual) 04/04
© 2004 Alamo Group Inc.
Port "D"
To Motor
Camplate
Piston Asy.
Case Drain
Neutral Adjustment
Servo Control Supply Oil
FIGURE 42 PUMP
System Relief &
Check Valve
System Relief
& Check Valve
91
Port "C"
From Motor
Gerotor
Charge
Pump
Charge
Pump
Suction
Charge
Pump
Relief
Valve