A4VTG Variable Closed circuit pumps , High pressure Axial piston
variable pump
Control device
HW – Proportional control hydraulic, mechanical servo
The output flow of the pump can be steplessly varied in the range
between 0 to 100 %, proportional to the rotation of the control
lever between 0° and ±29°.
A feedback lever connected to the stroke piston maintains the pump
flow for any given position of the control lever between 0° and
29°..
EP – Proportional control electric
The output flow of the pump can be steplessly varied in the range
between 0 to 100 %, proportional to the electrical current supplied
to solenoid a or b.
The electrical energy is converted into a force acting on the
control piston. This control piston then directs control hydraulic
fluid into and out of the stroke cylinder to adjust pump
displacement as required.
A feedback lever connected to the stroke piston maintains the pump
flow for any given current within the control range.
Technical data
Series 33.
Sizes NG71, 90.
Nominal pressure 400 bar.
Maximum pressure 450 bar.
Closed circuit.
For the drum drive in mobile concrete mixers.
Features
––Variable axial piston pump of swashplate design for hydrostatic
drives in closed circuit
––The flow is proportional to the drive speed and displacement.
––The flow increases as the angle of the swashplate is adjusted
from zero to its maximum value.
––Flow direction changes smoothly when the swashplate is moved
through the neutral position.
––Two pressure-relief valves are provided on the high pressure
ports to protect the hydrostatic transmission (pump and motor) from
overload.
––The high-pressure relief valves also function as boost valves.
––The integrated boost pump acts as a feed pump and control
pressure supply.
––The maximum boost pressure is limited by a built-in boost
pressure-relief valve.
