Variable displacement axial piston pumps are designed for use in in closed circuits, connected directly to motors. As following a basic schematic of an hydrostatic transmission with variable displacement axial piston pump and a fixed displacement axial piston motor.
The displacement is adjusted by means of a servo-control and an internal swashplate. The closed loop design allows the swashplate to incline infinitely between -18 degrees and +18 degrees.
The zero-degree position is the zero flow stand-by position, where the motor is not moving.
Various controls are available to adjust the flow (hence the speed) of the motor: manual lever operated, electric on/off, electric proportional, automotive, etc.
Closed loop pumps have a built-in charge pump that keeps the closed loop ring filled of oil, keeps a positive pressure in the main circuit (usually between 20 and 30 bar) and provides pilot pressure to the servo-control. Most pumps are supplied with maximum pressure relief valves, even though in some cases the valves are installed on the motor side (i.e. in concrete mixer systems)
Closed Loop pumps can be configured as single or tandem version and can have several through drive options, i.e . to fit auxiliary gear pumps.
Closed loop systems are the ideal solutions for mobile vehicles, such as harvesters, concrete mixers, loaders, compactors, etc.
Our specialized team will be able to recommend the right pump and control for your applications.