Heat exchanger core construction

A heat exchanger core for forming a first fluid path and a second fluid path which is fluid imperviously separated from the first fluid path and in heat exchanging relation therewith, said core comprising a plurality of first plate members and a plurality of second plate members, each of said first and second plate members being formed from a substantially rigid sheet metal material of constant thickness and shaped to define a planar plate with the first and second plate members being assembled alternately so that the plates lie in parallel stacked spaced relationship, the space between the plate of each first plate member and the plate of a next adjacent second plate member on one side defining a part of the first fluid path and the space between the plate of each first plate member and the plate of the next adjacent second plate member on an opposed side defining a part of the second fluid path, and a plurality of first and second connecting means, each first connecting means coupling one of said first plate members to the next adjacent second plate member on a respective side of said one of said first plate members and defining between said one of said first plate members and said next adjacent second plate members a first and a second guiding wall each bridging the space between said one of the first plate members and said next adjacent second plate member at a respective one of two parallel edges of said one of the first plate members and said next adjacent second plate member and forming side edges of said part of the first fluid path, each second connecting means defining between one of said first plate members and the other of said next adjacent second plate members a third and a fourth guiding wall each bridging the space between said one of said first plate members and said other of said next adjacent second plate members at a respective one of two parallel edges of said one of the first plate members which parallel edges are at right angles to the parallel edges of the first and second guiding walls, said third and fourth guiding walls forming side edges of said part of the second fluid path, each of said first, second, third and fourth guiding walls comprising an edge portion of one of said first and second plate members which is bent at an angle to the planar plate to which it is attached, and each of said connecting means including a pair of slot means each slot means of said pair being defined by one of said first and second plate members and being arranged along a respective edge of the other of said first and second plate members, each slot means comprising two slot sides and a slot base interconnecting the slot sides, said slot sides both lying parallel to the planar plate of that one of said first and second plate members by which the slot means is defined, the slot base being dimensioned so as to form between said slot sides a distance substantially equal to said thickness of the sheet metal material, and said slot sides receiving therebetween an edge portion of said respective edge of the other of said first and second plate members.