ENGLISH
is reached between the pressure that arises when the valve opens
and closes so that a low-load carrying spring can be used so that
no effort whatsoever is involved in opening the valve.
The pressure of the air flowing through the nozzle generates a re-
action on the part of the pad, which subsequently opens. The pad
is perforated as well and placed at the edge of the shaft, where
the pressure is contrasted by the combined force of the spring and
the air penetrating the balance chamber.
The end result of this in practical terms is a breathing effort reduced
to near inexistent levels, and an outstanding level of performance
even in very deep waters.
The adjustable Galaxy/Master second-stage regulator makes it
possible to modify the inhalation effort thanks to the external metal
knob, thus directly affecting inhalation resistance. In practice,
screwing the external knob clockwise increases inhalation resist-
ance whereas screwing it anticlockwise decreases inhalation re-
sistance. This regulation system includes two seals designed to
protect the water infiltration mechanism. When adequately lubri-
cated during manufacturing/maintenance phase, these seals pro-
tect the mechanism thread from the formation of oxide which
could stiffen or even block the rotation of the regulation knob.
This way, the knob remains consistently effortless and the subse-
quent adjustment of the inhalation effort can be achieved with pre-
cision and ease as the regulating mechanism thread remains
waterproof.
The Galaxy second-stage regulator (fig.9) doesn’t allow you to ad-
just the inhalation effort since it isn’t equipped with the regulation
mechanism. It does however include all the other features of the
adjustable Master version.
The adjustable nozzle is positioned inside the valve compartment
so that when the mechanism is opening, the air that comes out of
it is directed towards the mouthpiece thanks to the extremely pre-
cise and detailed design of the inner walls and casing of the regu-
lator.
In order to ensure the negative pressure isn’t too violent for the
body - which could potentially suck the diaphragm back in and
make the regulator to free-flow - there’s a diaphragm balance hole
inside the valve unit.
Once the airflow delivered through the injector and directed to-
wards the mouthpiece becomes consistent, it generates negative
pressure inside the regulator casing due to the increase in airflow
speed. This phenomenon of negative pressure called the “Venturi
effect”, keeps the diaphragm flat, which in turn significantly reduces
the inhalation effort of the diver.
The Venturi effect immediately ceases as soon as the diver stops
breathing; the diaphragm then reverts back to its normal position
and the lever, actioned by the spring, lifts up and makes the piston
touch the nozzle, which interrupts the passage of air.
In order to enhance the Venturi effect, both stages of Cressi-Sub
regulators are equipped with an air flow deflector which can be po-
sitioned two ways, as indicated by the etched scale on the casing:
In the first position, the flow-limitation device place in the mouth-
piece’s inlet duct, is actioned and the Venturi effect is stopped and
any free-flowing is prevented. In the “+” position however, the Ven-
turi effect is unrestrained and the air flow provided by the regulator
to the maximum level subsequently increases.
WARNING: always remember to keep the flow deflector
lever in pre-dive position (-) when the regulator is not in use; if
not, any accidental impact or pressure on the manual switch
when the regulator isn’t positioned inside the mouth, or if it is
63
SECOND STAGES
DIVE PRE-DIVE
fig. 12
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