Method of making a plate-type heat exchanger

Claim 1

A process for the soldering together of a stack of plates defining spaces between them to form a plate-type heat exchanger from the plates and wherein the spaces are formed as a plurality of passages of said heat exchanger running from one side of the stack to another side thereof generally along the plates, said method comprising the steps of: holding said plates together in a sealed chamber with solder disposed at junctions between them; passing a heating gas directly through said passages by distributing said gas thereto and thereby heating said plates, said heating gas being a gas inert with respect to the solder and said plates and being at a temperature below the melting point of said solder the heating gas traversing said passages before entering the chamber space around the held-together plates; thereafter only discharging the heating gas into the chamber space around the held-together plates; terminating the flow of gas through said passages; heating said chamber to a temperature above the melting point of said solder thereby causing said solder to flow and bond said plates together; and cooling said plates.