Abstract: A leakproof soldered joint between overlying surfaces of two pieces of metal which are riveted together to bring areas of said surfaces into intimate contact with one another all around the holes through which the rivets pass, said joint being achieved by a method which, before the riveting operation, involves placement of thin washers of solder between said pieces of metal in register with aligning rivet holes therein, to establish a slight space between said pieces, and after the riveting operation, applying molten solder to all of the marginal edges of said overlying surfaces of the two pieces of metal so as to cause it to flow by capillary action between the entire areas of said overlying surfaces, and utilizing the heat of the molten solder to melt said washers and thereby cause molten solder therefrom to flow into any and all interstices between the rivets and the edges of the holes through which they pass.

Abstract: A sectional heat exchanger having a frame for receiving and supporting a plurality of heat exchanger units which have a yieldingly compressible plate attached to the side of the unit and extending in abutment with each other for snugly retaining the units within the frame.