Iwao Yamamoto

Pneumatic Digital Amplifier with Positive Feedback System

Described in this paper, is a switching device based on a pneumatic amplifier with a positive feedback system. Two sets of bellows are located on the same axis in an enclosure, and divide it into three chambers. A nozzle is put on a movable end of one of the sets of bellows and faces the movable closed end of the other. The nozzle is pneumatically connected to a constant pressure source through an orifice provided in the fixed end of the former bellows, and its back pressure is used as the output of the device. The positive pulsating pressure introduced in the latter bellows serves as the input signal for setting the device and keeps the output pressure at a high level by the positive feedback action of the former bellows. The pressure within the enclosure serves as the input signal for resetting the device and causes the output pressure to fall off by compressing the both sets of bellows. Negative pulsating pressure can be also applicable as the input signals, where the pressure within the enclosure serves as the set signal and the pressure in the latter bellows as the reset signal. Experiments were conducted with an apparatus made on trial. The conditions of setting or resetting the device and the dynamical behavior were discussed using the results.

Pneumatic Micrometer with a Feedback Circuit

This paper is concerned with transfer characteristics of a pneumatic micrometer system with a negative feedback transducer. The system has two negative feedback pathes. One of them is based on the transfer characteristics of the feedback transducer which is introduced to linealize the transfer characteristic of the system and the other is caused by repulsive pressure force between nozzle and its counter face as an inevitable consequence of introducing the former. The feedback quantity through the latter is non-linear in relation to the output pressure but linear to the stiffness of the transducer. The total static transfer characteristic is shown as the sum of the transfer characteristics of the above two feedback circuits and of the basic pneumatic micrometer. The condition of reducing the above secondery feedback effect is discussed. Using a deviation ratio, defined by representing the transfer characteristic curve of the basic pneumatic micrometer circuit as a sum of an appropriate linear relation and the deviation from it, the linear range on the transfer characteristic curve of the system can be estimated from the feedback ratio of the feedback transducer, so far as the secondary feedback effect is small. The dynamic performance and an application of the principle are also described.