Assembly 1

Maximum pressure limiting (pressure relief valve function)

The pressure in the hydraulic system is limited to 250 ±5 bar (3625 ± 70 psi) in order to prevent damage to the components. This function is performed by the pressure regulator (4).

During normal operations (working pressure < max: pressure) pressure regulator (4) is pushed to the right, up against the stop by pressure spring (21).

If for example, a selective control valve is actuated and the cylinder reaches its end position, the load pressure at inlet port (2) rises until it is equal to the pressure at pump outlet port (16).

Under these pressure conditions:

Volumetric flow controller (3) is pushed to the right against the stop by pressure spring (17).

Pressure regulator (4) is pushed to the left, up to the stop against the force of pressure spring (21).

This movement takes place at a pressure of to 250 ± 5 bar (3625 ± 70 psi). Control edge (18) is opened so that the pump pressure acts on the upper side of control plunger (10).

The swash plate (13) is now moved to its ‘minimum delivery’ position against the force of control spring (11). This process takes 8-10 milliseconds.

The pump now delivers the minimum volumetric flow against the maximum pressure of to 250 ± 5 bar (3625 ± 70 psi).

The hydraulic system remains at the maximum pressure level until the selective control valve is moved to the neutral position.