Process of producing oxygen

Claim 1

A PROCESS FOR PRODUCING OXYGEN BY THE LIQUEFACTION AND RECTIFICATION OF AIR, WHICH COMPRISES, PASSING STREAMS OF OXYGEN AND NITROGEN PRODUCTS OF RECTIFICATION THROUGH SEPARATE PATHS IN AT LEAST TWO HEAT EXCHANGE ZONES CONNECTED IN SERIES, EACH OF SAID ZONES CONTAINING AT LEAST THREE PATHS IN HEAT EXCHANGE RELATION WITH EACH OTHER, PASSING A STREAM OF AIR AT ABOUT 70 TO ABOUT 85 POUNDS GAUGE THROUGH A THIRD PATH IN THE FIRST ZONE IN HEAT EXCHANGE RELATION WITH THE OXYGEN AND NITROGEN STREAMS FLOWING THROUGH THEIR RESPECTIVE PATHS IN SAID FIRST ZONE, EXPANDING A MINOR PORTION OF THE AIR LEAVING SAID FIRST ZONE AND IMPARTING THE REFRIGERATION THUS PRODUCED TO AT LEAST ONE OF SAID OXYGEN AND NITROGEN STREAMS FLOWING THROUGH SAID FIRST ZONE, PASSING THE REMAINDER OF THE AIR THROUGH A THIRD PATH IN THE SECOND ZONE IN HEAT EXCHANGE RELATION WITH THE OXYGEN AND NITROGEN STREAMS FLOWING THROUGH THEIR RESPECTIVE PATHS IN SAID SECOND ZONE, REGULATING THE FLOW OF AIR, NITROGEN AND OXYGEN INTO AND FROM SAID SECOND ZONE SO THAT THE TEMPERATURE WITHIN SAID SECOND ZONE IN SUCH AS TO EFFECT SUBSTANTIALLY COMPLETE REMOVAL OF CARBON DIOXIDE FROM THE AIR IN ITS PASSAGE THROUGH ITS PATH IN SAID SECOND ZONE AND THE DIFFERENCE BETWEEN THE TEMPERATURE OF THE AIR AND THE WEIGHTED AVERAGE TEMPERATURE OF THE NITROGEN AND OXYGEN AT THE COLDER END OF SAID SECOND ZONE FALLS WITHIN THE RANGE OF ABOUT 5* TO ABOUT 10* F., AND PERIODICALLY REVERSING THE FLOW OF AIR AND NITROGEN THROUGH THEIR RESPECTIVE PATHS IN SAID ZONES, THE AIR UPON REVERSAL FLOWING THROUGH THE PATHS THROUGH WHICH HAD PREVIOUSLY FLOWED THE NITROGEN AND THE NITROGEN FLOWING THROUGH THE PATHS THROUGH WHICH HAD PREVIOUSLY FLOWED THE AIR, WHEREBY UPON EACH REVERSAL THE NITROGEN SUBSTANTIALLY COMPLETELY REMOVES THE CARBON DIOXIDE DEPOSITED IN SAID SECOND ZONE DURING THE PRECEDING STEP OF THE PROCESS.