Abstract
Described in this paper, is a pneumatic logic device which can function as AND gate with Schmitt-trigger.
Four sets of bellows are bult in an enclosure with a vent. Two of them, whose movable ends are formed as a nozzle, are connected pneumatically to a constant pressure source through an orifice. The other two sets of bellows have a movable closed end individually and input pressures are introduced in the bellows through input ports provided in their fixed ends. Each one of the former sets of bellows are located on the same axis to one of the latters. The nozzles and the movable closed ends which are arranged as the counterface of the nozzles operate as a nozzle-flapper system in connection with the orifice, and the output pressure changes corresponding to the total value of the gaps between the nozzles and their counter-faces. When either or both of the input pressures is low, the output pressure maintains low level since the total gap remains in a appreciable large value. When high pressure is introduced in both input ports, the nozzles contact the movable closed ends and the output pressure maintains a high level equal to the supply pressure. Because of the positive feedback action of the former sets of bellows, Schmitt-trigger operation accompanies the above logical operation and switching of the output pressure with abrupt slope can be performed.
