Refrigeration system for low temperature operation

Claim 1

THE COMBINATION IN A REFRIGERATION SYSTEM UTILIZING A LOW BOILING POINT REFRIGERANT WHICH FLOWS IN A CLOSED CYCLE THROUGH SAID SYSTEM AND INCLUDING AN EVAPORATOR, A CONDENSER, A FIRST LINE BETWEEN SAID EVAPORATOR AND SAID CONDENSER FOR CONDUCTING REFRIGERANT FROM SAID EVAPORATOR TO SAID CONDENSER, A SECOND LINE BETWEEN SAID EVAPORATOR AND CONDENSER FOR CONDUCTING REFRIGERANT FROM SAID CONDENSER TO SAID EVAPORATOR, MEANS IN SAID FIRST MENTIONED LINE FOR COMPRESSING THE REFRIGERANT FLOWING THERETHROUGH, AND MEANS IN SAID SECOND LINE FOR EXPANDING THE REFRIGERANT FLOWING THERETHROUGH, OF A BY-PASS LINE FOR WITHDRAWING LIQUID REFRIGERANT FROM SAID CONDENSER, A PUMP IN SAID BY-PASS LINE OPERABLE TO BOOST THE PRESSURE OF THE WITHDRAWN REFRIGERANT ABOVE THE CONDENSER PRESSURE, A VALVE IN SAID BY-PASS LINE OPERABLE TO PREVENT OR PERMIT FLOW OF REFRIGERANT THERETHROUGH, AND A CHECK VALVE IN SAID SECOND LINE BETWEEN SAID CONDENSER AND SAID EXPANSION MEANS FOR PREVENTING REVERSE FLOW THROUGH SAID LATTER LINE, THE DOWNSTREAM END OF SAID BY-PASS LINE BEING CONNECTED WITH SAID SECOND LINE BETWEEN SAID CHECK VALVE AND SAID EXPANSION MEANS SO THAT THE WITHDRAWN REFRIGERANT IS PREVENTED BY SAID CHECK VALVE FROM RETURNING TO SAID CONDENSER AND IS CAUSED INSTEAD TO FLOW THROUGH SAID EXPANSION MEANS TO SAID EVAPORATOR TO INITIATE NORMAL FLOW THROUGH THE SYSTEM.