This is a sphere separated into two parts by an elastic membrane (m)

- The top part is filled with nitrogen under pressure

- The lower part is always in contact with the fluid from the pressure regulator.

At rest, the membrane (m) rests on its stop under an initial nitrogen pressure of 65+/-5 kg/cm2.

Charging

Initially, after fall of pressure in the circuits, pressure remains in the assembly: (fig.1)

- Chamber (A): pressure = 65+/-5 kg/cm2

- Chamber (B-C-D): atmospheric pressure.

After the engine is started (fig.2), the liquid driven back by the pump passes through chamber (C) of the pressure regulator and directs itself towards the circuit where it is to be used by raising the non-return valve (a) and the membrane (m); the volume of gas decreases and the pressure increases in chambers (A-B-C):(D) always remains at atmospheric pressure (connected with the tank).

Discharging (fig.3 and 4)

The piston is subjected to the opposite forces:

On its upper face: force (F) has the action of existing pressure (P) in the chambers (A-B-C).

On its lower face: The sum of two forces:

Force (R) is under the action of the spring.

Force (r) is under the action of pressure (P) existing in the chamber (C) and acts on (S).

The discharging takes place when (F) is higher than (R+r). At this point the non-return valve (a) is closed again and the piston, after detachment from the ball (b), goes down while compressing its spring. The pressure in chamber (C) falls and the pump drives back to chamber (D).

Consumption of Fluid - After consumption of fluid under pressure in the systems:

- existing pressure (P) in chamber (B) decreases.

- the piston pushed by its spring goes up gradually.

When (F) becomes lower than (R), the ball (b) is returned to its seat and the non-return valve (a) opens: the pump pressurises the chambers (C and B), the cycle continues.

Foot-note: The pressure regulator possesses a bleed screw that makes it possible to lower the pressure in the accumulator and the circuits (see Pl.7)