Circuits for stabilising ultrasonic generator and preventing drying - in prodn. of aerosols for breathing machines

摘要

An ultrasonic generator producing an aerosol in a gas by atomising liq. with a mechanical vibrator supplied with a variable power high frequency signal produced by an oscillator circuit has a protector to prevent damage to the vibrator on dry running and which stabilises the signal during wet running. The vibrator protector has a circuit which detects changes in at least one parameter in the vibrator circuit caused on transition from wet to dry running. The wet running detector circuit includes transistors, esp. in the amplifier section which may be self-excited or externally excited. The air supplied by medical breathing appts. must be kept moist by an aerosol to prevent the patient's air passages drying out, and this appts. must respond to changes, e.g. in the patient's condition or in the viscosity of the commonly used water/oil mixture. The present appts. reduces the need for constant medical observation.