Abstract
This paper is concerned with a new moving parts pneumatic NAND gate based on a nozzle flapper system with a positive feedback mechanism.
Two nozzles are built in an enclosed chamber and each of them counterfaces one of the movable closed ends of two sets of bellows placed in the chamber. Air is fed from a constant pressure source into the enclosed chamber through the nozzles and then flows out to the atmosphere through an orifice provided on the chamber wall. Input pressures are introduced in the sets of bellows and the pressure in the chamber serves as output of the device. The pneumatic circuit which is constructed of the nozzles, the orifice and the sets of bellows is arranged to have bi-stable transfer characteristics, which is caused by a positive feedback action of the bellows. When either or both of the input pressures are low, the output pressure maintains high pressure level nearly equal to the supply pressure, since the fluid resistance between the chamber and the supply source is low. When the pressure in both of the sets of bellows reaches a high level, both of the movable closed ends contact the nozzles and the output pressure falls down to the atmospheric pressure due to shutting off the air flow through the nozzles. Transitions of the output pressure between the two levels can be sharply performed with the positive feedback action.
