Plate type heat exchangers

Claim 1

A PLATE TYPE HEAT EXCHANGER COMPRISING A PLURALITY OF SUBSTANTIALLY RECTANGULAR FLAT SHEETS STACKED IN SPACED RELATIONSHIP AND SPACED FROM ONE ANOTHER BY CORRUGATED SHEETS OF SUBSTANTIALLY THE SAME DIMENSIONS AS SAID FLAT SHEETS, SOME OF SAID CORRUGATED SHEETS BEING ARRANGED TO HAVE THEIR CORRGUATIONS EXTEND IN A DIRECTION SUBSTANTIALLY NORMAL TO THE DIRECTION OF THE CORRUGATIONS OF OTHERS OF SAID CORRUGATED SHEETS, SAID CORRUGATIONS FORMING FLOW CHANNELS FOR HEAT EXCHANGING FLUIDS, LOCATING RODS PASSING THROUGH THE FLAT SHEETS AND THE CORRUGATED SHEETS AT CORNERS THEREOF TO SEAL THE FLOW CHANNELS DEFINED BY THE OUTER CORRUGATIONS FROM EACH OTHER, AND LOCATING RODS HAVING PART OF THEIR SURFACES EXPOSED, AND AT LEAST ONE HEADER FOR FLUID PASSING TO OR FROM SOME OF SAID FLOW CHANNELS, SAID HEADER HAVING WALL EDGES WHICH EXTEND ALONG AND ARE BOUNDED TO THE EXPOSED SURFACES OF SAID LOCATING RODS.