Heat transfer plate construction

Claim 1

A PLATE TYPE HEAT EXCHANGER COMPRISING A PLURALITY OF PLATES COMPRISING A FIRST SET OF ADJACENT PLATES DEFINING FIRST SPACES INTERMEDIATE EACH PAIR OF SAID ADJACENT PLATES, SAID PLURALITY OF PLATES FURTHER COMPRISING A SECOND SET OF ADJACENT PLATES DEFINING SECOND SPACES INTERMEDIATE EACH PAIR OF SAID LAST-NAMED PLATES, SAID PLURALITY OF PLATES INCLUDING AT LEAST ONE PLATE COMMON TO SAID FIRST SET AND TO SAID SECOND SET, SAID FIRST SPACES BEING ADAPTED FOR FLOW THERETHROUGH OF A HIGH-PRESSURE MEDIUM, SAID SECOND SPACES BEING ADAPTED FOR FLOW THERETHROUGH OF A LOW-PRESSURE MEDIUM, SAID HEAT EXCHANGER FURTHER COMPRISING FIRST UNDULATED SHEET METAL STRIPS IN SAID FIRST SPACES HAVING FLAT PORTIONS SECURED TO SAID FIRST-NAMED ADJACENT PLATES AND FORMING A PLURALITY OF CHANNELS IN THE DIRECTION OF FLOW OF SAID HIGH PRESSURE MEDIUM, SAID STRIPS BEING SPACED FROM EACH OTHER IN THE SAID DIRECTION OF FLOW OF SAID HIGH PRESSURE MEDIUM, SAID HEAT EXCHANGER FURTHER COMPRISING SECOND UNDULATED SHEET METAL STRIPS IN SAID SECOND SPACES SECURED TO SAID ADJACENT PLATES OF SAID SECOND SET, SAID SEC-