BIRD MARK 7 - Page 8

PNEUMATIC
SYSTEMS
SECTION
4:
PNEUMATIC SYSTEMS
INSPIRATORY PRESSURE LIMIT
ZERO ENTRAINMENT
DECREASED GAS FLOW DUE
TO PNEUMATIC CLUTCH
FLOWING AGAINST INITIAL PULMONARY
RESISTANCES NORMAL PRESSURE RISE
Macosn
map
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FIGURE 5
. FLOW CARTRIDGES
The design of the flow cartridges evoived as a
result of the need to direct gas flows within a
ventilator. Three cartridges are currently available
for this function:
1. Normally open cartridge.
2. Normally closed cartridge.
The NORMALLY OPEN CARTRIDGE is designed
to allow gas to flow through the system until a
pressure is introduced into the back of the car
tridge at the servo port (Fig. 6). Once the cartridge
is pressurized, the
diaphragm exerts suffi-
cient force to overcome a
spring tension and the
valve closes completely,
blocking all flow (Fig. 7).
As long as the cartridge is
pressurized, no flow of gas
is allowed. Once the clos-
ing pressure is released,
the spring tension over
comes the pressure and
gas is allowed to flow
through the system.
FIGURE 7
The NORMALLY CLOSED CARTRIDGE is similar
to the normally open cartridge in many ways. Sev-
eral of the components are interchangeable. The
maior difference in function is that pressurization of
the diaphragm opens the cartridge from a closed
position allowing gas flow through the system (Fig.
8). Pressure exerted on the master diaphragm will
insure a Continual flow. Once the pressure is
decreased, the spring tension resets the poppet
and the gas is blocked at the inlet of the cartridge
(Fig. 9).
INLET PORT
FIGURE 8 FIGURE 9
@ METERING MANIFOLD AND
NEEDLE VALVE
The METERING MANIFOLD is utilized in Bird
equipment to distribute source gas to three ports.
The primary port is intended to give the clinician,
in conjunction with the needle valve assembly, vari-
able flows of gas through the ventilator (Fig. 10).
The remaining two ports are utilized for accessory
distribution of source gas to other circuits within
the equipment. :
ACCESSORY POAT
FIGURE 10
Gas entering the inlet stem is varied, as it flows
through the metering port, by an adjustable needle
valve (Fig. 11).
INLET STEM
FIGURE 11
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