(8) Compound-lockout cartridge. The compound-lockout cartridge (A in
figure 1-7) consists of a double diaphragm, a spring-loaded poppet valve with four gas
connections, and an adjustable screw on one end for calibration of the lockout function.
The flow through the lockout cartridge also goes to a lockout alarm. A tee connection is
installed in the inlet power line of the Mark 2 servo, which delivers source-gas pressure
from the mode selector valve to the inlet side of the inspiratory-lockout cartridge. Flow
out of the cartridge is directed to a tee fitting and to the pneumatic alarm. Its function is
to terminate inspiration when the inspiratory time limit is exceeded and sound an alarm.
Figure 1-7. Compound-lockout cartridge (A), low pressure alarm (B), and self-test
(9) Low pressure alarm. The fifth and sixth outlets from the inlet manifold
deliver source gas to a pneumatically-operated, low pressure alarm cartridge (B in
figure 1-7). It functions on the spring balanced diaphragm principle. When source
pressure against the diaphragm drops below the value required to keep the valve closed
against the tension of the opening spring (below 43psi), the valve opens, allowing direct
flow to the alarm. There are two flow paths to the low pressure alarm. One operates the
diaphragm, the other operates the pneumatic alarm.
(a) Peak inspiratory pressures are controlled by adjusting venturi output
pressures directed to a diaphragm in the outflow valve. Venturi output pressure is
controlled by the inspiratory relief pressure control, an unrestricted needle valve with a
bleeder port which controls the gas mixture pressure delivered to the venturi.
(b) Considered part of the spoiler assembly, the inspiratory relief
pressure control, maintains a single operational pressure at the inspiratory interrupter
cartridge diaphragm to ensure stable operation during controlled IMV.