Synchronized feed type oxygen concentrator for use in an open breathing system

Claim 1

In an open breathing circuit including a gas supply system and a breathing system of a human being or the like, said gas supply system supplying oxygen enriched gas produced from ambient air to said breathing system in synchronization with a breathing motion of said human being or the like through an open air type breathing system, comprising: synchronized feed type oxygen concentration means for supplying oxygen enriched gas to said breathing system in synchronization with said breathing motion of said human being or the like, including: thermocouple sensor means adapted to be positioned close to the nostrils of said human being or the like for generating an detection signal indicative of the instantaneous temperature of a breathing air flow of said human being or the like; and control means, coupled to said thermocouple sensor means, for detecting the beginning of an inhalation phase in a breathing cycle of said human being or the like by detecting substantially the beginning of a drop in temperature indicated by said detection signal, and for controlling said gas supply system so as to supply oxygen enriched gas to said breathing system only during said inhalation phase, said control means including: amplifier circuit means, coupled to an output of said thermocouple sensor means, for amplifying a voltage level of said detection signal to a desired level; holding means, coupled to an output of said amplifier circuit means, for holding a first voltage level of the amplified detection signal from said amplifier circuit means, said first voltage level being the voltage level of an output of said amplifier circuit means at a given moment; comparator means, coupled to an output of said amplifier circuit means and to an output of said holding means, for comparing a second voltage level of said amplified detection signal with said first voltage level, said second voltage level being the voltage level of said amplifier circuit means at the moment when a predetermined period of time has passed since said first voltage level started to be held, and for generating an enabling pulse beginning the supply of gas when the absolute value of said second voltage level is less than the absolute value of said first voltage level, said first voltage level absolute value being arranged to be less than the absolute value of a predetermined portion of the maximum absolute value of said detection signal voltage level; and bistable means coupled to an output of said comparator means and being switched by said enabling pulse to a first state for commencing said supply of gas, and being switched to a second state for halting said supply of gas, thereby continuing to supply said gas for the duration of said inhalation phase.