Patent ID: 7404434

Claim:
A heat exchanger comprising a plurality of plates arranged in a stack, with fluid flow passages being provided between adjacent plates in the stack, each of the plates comprising: (a) a plate bottom having a top surface and a bottom surface, the top surface facing upwardly and the bottom surface facing downwardly, the plate bottom having a peripheral edge; (b) a continuous plate wall extending upwardly and outwardly from the peripheral edge of the plate bottom; (c) a first inlet hole and a first outlet hole provided through the plate bottom, the first inlet and outlet holes being spaced from one another and spaced from the peripheral edge of the plate bottom; (d) a second inlet hole and a second outlet hole provided through the plate bottom, the second inlet and outlet holes being spaced from one another, spaced from the first inlet and outlet holes, and spaced from the peripheral edge of the plate bottom, wherein the second inlet and outlet holes are spaced upwardly relative to the first inlet and outlet holes; (e) a pair of raised bosses having upper surfaces in which the second inlet and outlet holes are provided, the upper surface of each said boss surrounding one of the second inlet and outlet holes and having an outer edge which, for a first part of its length, is joined directly to the plate wall; and (f) a pair of ribs, each of the ribs comprising a first end, a second end and an intermediate portion extending between the ends, the intermediate portion comprising a rib side wall and a rib upper surface; each of the ribs extending along the plate wall, the first end being joined to one of the bosses, the intermediate portion located between the plate wall and one of the first inlet and outlet holes, the intermediate portion extending from a side of said hole which is proximal to the first end of the rib to a side of the said hole which is distal to the first end of the rib, the second end of the rib being located at the distal side of the hole and being joined to the plate bottom; wherein the plates in said stack are in nested, sealed engagement with one another, with the plate bottoms of adjacent plates being spaced from one another to form said fluid flow passages, with the first inlet and outlet holes in each plate being aligned with the second inlet and outlet holes, respectively, of an adjacent plate, and with the upper surfaces of the bosses in each plate sealingly engaging the bottom surface of an adjacent plate; wherein directly joining the upper surfaces of the bosses to the plate wall prevents fluid from flowing between the outer edge of each of the bosses and the plate wall; and wherein the upper surface of each rib engages a bottom surface of one of the bosses of an overlying plate.