Abstract
Described in this paper, is a multivibrator, which can generate a continuous train of pneumatic square wave.
Two diaphragms are located in an enclosure which opens by an exhaust vent to the atmosphere. The centre of one of the diapharagms (feedback diaphragm) is a nozzle and faces the centre surface of the other (control diaphragm). The inside chamber of the feedback diaphragm is connected to the air supply chamber through an orifice provided in the fixed part of the diaphragm. The fluidic circuit which is composed of the nozzle, the orifice and the feedback diaphragm is so arranged to have bi-stable characteristics. A restrictor connects the supply chamber to the inside of the enclosure, and the feedback diaphragm chamber is also connected to the 3rd diaphragm chamber through an adjustable restrictor. A flate plane fixed on the 3rd diaphragm controls the flow-out area of the exhaust vent. Output wave is generated as follows.
First, when the supply pressure is introduced in the device, the nozzle contacts its counterface and the output pressure maintains a high level equal to the supply pressure. Then, the 3rd diaphragm pressure increases with a speed given by the resistance of the adjustable restrictor and the capacity in the 3rd diaphragm chamber. The enclosure pressure increases following to the increase of the vent resistance caused by the pressure change in the 3rd diaphragm chamber. When the enclosure pressure reaches a constant level, the nozzle separates abruptly from its counterface and the output pressure falls down to a low level. Then, the 3rd diaphragm pressure turns to decrease, and the enclosure pressure decreases following to the decrease of the vent resistance. When the enclosure pressure reaches to a low level, the nozzle contacts its counterface and the output pressure increases to the high level. The repeat of above process produces the pneumatic pulse train.
