Apparatus for controlling environmental conditions, suitable for use underwater

Abstract

Abstract The subject of the invention described in the following specification relates to the problem of maintaining a safely breathable oxygen-containing atmosphere. Thus, the invention is especially useable under abnormal environmental conditions where it is necessary to provide and control an atmosphere suitable therein. The disclosed illustrative embodiment is a selfcontained closed circuit-type underwater breathing apparatus for diver use. A plurality of oxygen sensor cells, preferably at least three, each thermistor temperature compensated, are exposed to the gas stream in the system, each providing a current resulting in voltage drop across the thermistor, directly related to oxygen concentration which voltages then are amplified and electronically processed to operate oxygen supply means, which is a solenoid valve, whereby oxygen partial pressure is constantly maintained within a predetermined range. In the processing, the amplified voltages are electronically mathematically averaged and processed to deliver a single control signal to the solenoid. The system is adjusted at atmospheric pressure to provide one-half atmosphere oxygen partial pressure at a selected voltage level, e.g. about 2.4 volts average amplified cell voltage. As the quantity of oxygen thereafter varies in use by the diver, the average voltage varies linearly and the solenoid acts responsively thereto. Each amplified cell output is also connected into an alarm circuitry so that should any cell (or two or more) provide a voltage corresponding to oxygen partial pressure below or above a predetermined safe oxygen range, an audible alarm is sounded as a warning that something is wrong in the system. Separate visual oxygen partial pressure indicators are connected into the circuitry at the electronic amplification stages so that the diver may observe the individual indications provided by each of the sensor cells and, thereupon, determine the emergency remedial steps necessary to be taken. In the exemplary three-sensor system, the probability of simultaneous or close timewise malfunctioning of more than one sensor or its directly associated circuitry is extremely low - so low that in practical use it may reasonably be taken as zero. Consequently, the diver, while of course, recognizing the remote possibility of such a plural maloccurrence, may, and in practice will, presume any two similar partial pressure indicators correctly to reflect the actual internal conditions of the system - unless, of course, his own understanding of the particular situation might rarely permit a different conclusion. Contemplating most importantly such a single maloccurrence (thereupon resulting in an alarm sounding and indications from the meters that one of the voltage inputs is spurious) the design of the system, involving as it does the aspect of solenoid valve control by the average voltage, is such that the electronic circuitry responds to limit, or stabilize, the effect of the spurious voltage input upon the average voltage. This is accomplished via transistor clipping circuitry and an associated regulated pg,3 voltage source. Thereupon a nonvarying voltage, which is not outside the selected range for acceptable and safe oxygen partial pressure, constantly appears in the average voltage. Accordingly, the effective average voltage is then within the safe range aNd continues effectively to operate and to maintain a suitable oxygen partial pressure as long as the signals from the remaining cells are developed and delivered and they themselves are a correct measure of the oxygen partial pressure actually in the system. The system contemplates also an adjunctive, separate and exteriorly attachable sensor-indicator means by which the system may be further verified whereby the security of the diver is much enhanced. The system includes inert gas supply means which may be manually or automatically operated for supplying the remaining gas volume and pressure necessary for breathing underwater. By these and other means, the safety for the diver is enormously increased and the purpose of his dive can be accomplished under a minimum of constraint.

Inventors

• 👤 John W Kanwisher
• 👤 Walter A Starch

Bibliographic Details