Co2 freezeout system

Claim 1

IN AN ENVIRONMENTAL CONTROL SYSTEM FOR A SEALED COMPARTMENT CONTAINING AIR SUBJECTED TO CONTAMINATION OF CARBON DIOXIDE, MEANS FOR SEPARATING CARBON DIOXIDE FROM SAID AIR BY CONDENSATION OF CARBON DIOXIDE TO A SOLID FORM, SAID MEANS COMPRISINGING AN AIR COMPRESSOR, AN EXPANDER DRIVING SAID COMPRESSOR, A PRIMARY HEAT EXCHANGER TO COOL AIR AFTER COMPRESSION, FIRST, SECOND, THIRD AND FOURTH HEAT EXCHANGERS, MEANS FOR DEFINING A FLOW PATH FOR SUCCESSIVELY PASSING FLOW FROM SAID COMPARTMENT TO SAID PRIMARY HEAT EXCHANGER TO SAID FIRST HEAT EXCHANGER TO SAID SECOND HEAT EXCHANGER TO SAID THIRD HEAT EXCHANGER TO SAID FOURTH HEAT EXCHANGER BACK TO SAID SECOND HEAT EXCHANGER AND THROUGH THE EXPANDER, SAID THIRD AND FOURTH HEAT EXCHANGERS ADAPTED TO SEPARATE CARBON DIOXIDE FORM THE COOLED AIR BY FURTHER COOLING AND FREEZING OF CARBON DIOXIDE, AND MEANS DEFINING A RETURN FLOW PATH FOR RETURNING SAID CARBON DIOXIDE FREE AIR FROM SAID EXPANDER THROUGH SAID THIRD HEAT EXCHANGER AND TO SAID COMPARTMENT WHEREBY THE CARBON DIOXIDE FREE AIR IS UTILIZED AS THE LOW TEMPERATURE SOURCE FOR INDIRECT HEAT EXCHANGER WITH THE AIR IN SAID SECOND HEAT EXCHANGER.