Pneumatic Phase Controlled Rectifier with Positive Feedback System

Abstract

Described in this paper, is a pneumatic control device, which can perform similar operation to that of the silicon controlled rectifier in electronics. Two sets of bellows are located on the same axis in an enclosure which is opened to the atmosphere by an exhaust vent, and they devide the enclosure into three chambers. A nozzle opens at the movable end of one of the sets of bellows and faces the movable closed end of the other set. The back pressure chamber of the nozzle is connected to a pressure supply chamber through an orifice at the fixed end of the bellows mentioned first, and the back pressure serves as the output of the device. The nozzle, the movable closed end, the orifice and the bellows constitute an pneumatic micrometer circuit with positive feedback system. The pneumatic circuit is so arranged as to have bi-stable transfer characteristics over a wide range of supply pressure.
An alternating pressure is introduced to the supply chamber as the exciting signal to the device, and a pressure pulse synchronized with it is put in the bellows with the closed end as the control signal. In the absence of the control signal or during the period when the alternating signal is negative, the output pressure maintains a low level. If the control signal is put in during the period when the alternating pressure is positive, the output pressure steps up from the level to a high pressure level which is equal to the supply pressure. Removal of the control signal fails to turn the output pressure off, and the output maintains the high pressure level until the supply pressure falls down to zero. By controlling the timing of the control signal to the alternating pressure, the rectified and phase controlled pressure signal to the alternating pressure can be obtained as the output of the device.