Cressi MC7 Manuel D'instruction page 39

38 SECOND STAGES
When the air flow supplied into the injector and directed to the
mouthpiece becomes dense, it undergoes, as we mentioned
above, an acceleration known as Venturi effect. The consequent
vacuum which is created inside the second stage, keeps the
diaphragm depressed, thus virtually reducing the breathing
effort to zero.
The Venturi effect immediately stops as soon as the diver stops
breathing. The diaphragm returns to its normal position, the lever
comes up again pushed by its spring, and the nozzle is closed by
the piston.
In order to optimize the Venturi effect, Ellipse is provided with a
new and ergonomic flow deflector which has two operating
positions, clearly shown by the symbols on the regulator hous-
ing: "-" ("pre-dive" position) and "+"("dive" position). At the first
position, a flow limiting device placed in the mouthpiece inlet
starts operating and inhibits the Venturi effect, preventing a con-
stant flow. At the "+" position, the Venturi effect works at its best,
increasing the air flow supplied to the regulator to the maximum
level.
WARNING: Remember to always set the lever of the flow
limiting device to the pre-dive (-) position when the regulator is
not used, otherwise one of the following situations may cause
an even strong constant flow producing high air consumption:
an accidental impact, the regulator falling into water, pressing
the manual regulation purge button when the regulator is not
inside the mouth or suddenly taking the regulator out of the
mouth.
The dive (+) position must only be used while diving and only
when the regulator is inside the mouth.
fig. 8
DIVE
When the diver exhales, he/she causes the pressure to
increase inside the regulator second stage, which opens the
exhaust valve. The exhaust valve, has a large cone shape. The
newly designed exhaust tee is formed directly from the second
stage, thus creating an extremely compact assembly with an
extraordinary design. Air fed to the sides of the exhaust valve
seat, in the regulator second stage, protects the valve against
water turbulence which might lift it when the second stage
inside is depressurized, causing flooding. Moreover, a special
bulkhead on the second stage exhaust tee center line suitably
pushes the exhaust valve on its middle section, ensuring a bal-
anced opening.
PRE-DIVE
fig. 9