| 摘要 |
A commutator feeding device for a demand valve, comprising a transducer adapted for controlling the movement of a shutter element for feeding predetermined quantities of air into a chamber of said demand valve in response to a pressure variation taking place inside said chamber, said transducer being activated following the shifting of a deformable membrane. The device comprises a spring, disposed inside a small piston, adapted for resting on said membrane, said small piston being provided with radial stakes or spokes, each one of which is adapted to rest on the active surface of a corresponding helicoidal profile cam, with manually operable actuating means being predisposed for controlling the rotation of said small piston around its own axis, and hence the axial shifting of the small piston itself in the spring-compressing sense.
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