Heat exchanger

A heat exchanger comprising a rectangular exchanger pack which consists of a plurality of individual, mutually spaced, foil-type plates which have triangular corner notches and are connected with one another in sealed manner on marginal strips which extend between the corner notches in pairs on two opposite plate margins for the formation of alternately crossing flow-through passages between the plates, and comprising a frame housing surrounding the exchanger pack comprising two covers disposed adjacent the outer plates of the exchanger pack and four struts connecting the covers at their corners. The marginal strips to be connected of each two adjacent plates of the exchanger pack rest flatly upon each other and are mechanically connected with each other by folding over at least once. The struts of the frame housing define a triangular recess on their side facing the edge of the exchanger pack. The pack edges with the corner notches project into these recesses. The recesses on the struts are filled out with a sealing filling made of a moulding resin to beyond the corner notches.

The invention relates to a heat exchanger having a rectangular exchanger 
pack consisting of a plurality of individual, mutually spaced, foil-type 
plates which have triangular shaped corner notches and are connected with 
one another in sealed manner on the marginal strips extending between the 
clipped-out corner notches, by pairs at two opposite plated edges, to form 
alternately mutually crossing throughflow passages between the plates, and 
having a frame housing surrounding the exchanger pack, which housing 
consists of two covers lying adjacent the outer plates of the exchanger 
pack and four struts connecting the covers at their corners. 
In the plate-type heat exchanger according to German Offenlegungschrift OS 
25 21 351 and OS 25 33 490, the cross-flow exchanger pack consists of a 
single thin-walled strip, for example aluminum foil, cut to shape and 
folded in a special manner, where each two adjacent plates stick together 
and are connected by a common folded edge at one plate margin and at the 
opposite plate margin are bent towards one another and connected in sealed 
manner with one another along their line of contact by an adhesive 
connection. In this case the difficulty has arisen of adhering the plate 
margins with one another in such a way that the plate margins, held 
together only by the adhesive connection, cannot come apart and no 
leakages of the throughflow passages of the exchanger pack can occur. It 
has proved relatively expensive to cut the strip to shape and to fold it 
in such a way that the plates are spaced from one another and in 
connection with this the margins of a plate which meet in one plate corner 
are crimped to opposite sides for the formation of the common fold edge 
with the one adjacent plate and for the formation of the adhesive 
connection with the other adjacent plate. In this folding of the strip, 
triangular notches or clipped-out portions arise at the edges of the 
exchanger pack. In order to seal the crossing throughflow passages from 
one another at the edge of the pack, triangular sealing strips made of an 
elastic material, which engage in sealing manner in the clipped-out 
portions, are arranged on that side of the struts of the frame housing 
which faces the pack edge. It has proved difficult to obtain a durably 
elastic and satisfactorily sealing effect of the sealing strips, for 
example, under extreme temperature effects or in the case of aggressive 
media. Another heat exchanger of the initially stated type is known for 
example from the U.S. Pat. No. 1,635,838, where the exchanger pack 
consists of individual plates stacked one upon the other. The plates 
possess triangular clipped-out notches at their corners, so that marginal 
strips of the plates arise, which strips extend between the corner 
notches, which are bent off in alternating sequence and bent towards one 
another in pairs and come into contact at the margins. In the case of this 
heat exchanger the plates are clamped together by a plurality of clamping 
screws penetrating the exchanger pack, in order to hold together and 
compress the plate margins which are curved towards one another, and a 
welding of the mutually contacting plate edges is necessary in order to 
obtain a satisfactory sealing of the throughflow passages. The struts of 
the frame housing have an approximately rectangular cross-section and 
extend with an edge of its profile cross-section into the corner notches 
of the plates. In order to separate the mutually crossing throughflow 
passages from one another in sealed manner at the pack edges, a sealed 
welding-in of the profile edge of the struts is necessary in the corner 
notches of the plates. The production of this heat exchanger is also 
cumbersome and expensive. 
The invention provides a heat exchanger of the kind as initially stated, 
the production of which is simpler and cheaper and in which nevertheless 
the sealing of the throughflow passages of the exchanger pack along the 
plate margins and along the pack edges, and respectively, the frame 
housing struts is stable, reliable and durable. The formation of the heat 
exchanger in accordance with the invention resides in that the marginal 
strips to be connected of each two adjacent plates of the exchanger pack 
rest flatly one upon the other and are mechanically connected with one 
another by at least one folding over in the manner that the struts of the 
frame housing have a triangular recess on their side facing the edge of 
the exchanger pack, into which there project the pack edge with the corner 
notches of the plates and the depth of which recess is greater than the 
depth of the corner notches, and that the recesses in the struts are 
filled out to over the corner notches with a sealing filling made of 
moulding resin.

The rectangular exchanger pack 1 of the heat exchanger comprises a 
plurality of individual plates 2 stacked one upon the other, of which 
three plates are illustrated in FIG. 1. The plates 2 are punched or 
stamped out from a thin-walled material, for example, an aluminum foil. 
The plates 2 have pressed-in spacer ribs 3 which hold the plates at a 
desired distance from one another. The exchanger pack 1 is surrounded by a 
frame housing which comprises two covers 4 lying adjacent the two outer 
plates of the exchanger pack, and four struts 5 connecting the covers at 
their corners. The plates 2 are provided with triangular notches 6 at 
their corners. Thus marginal strips 7 of the plates 2 arise which extend 
between the corner notches 6 and the two marginal strips of a plate which 
respectively in each case run together into a corner notch can be bent 
over to opposite sides, as may be seen from FIG. 1. The depth of the 
corner notches 6, taking into account of the spacing of the plates, is 
dimensioned so large that the marginal strips 7 of two adjacent plates 2, 
which strips are bent towards one another, not only contact at their 
margins, but also, as illustrated by FIG. 1, lie flat upon one another and 
can be folded over together at least once. Due to this folding over 
portion 8, which can be produced very simply with a roller folding 
machine, the plates are mechanically connected with one another at their 
marginal strips and thereby held together firmly as well as in sealed 
manner. The marginal strips 7, as shown by FIG. 2, preferably are 
connected with one another by folding over twice, as double fold, whereby 
a particularly high strength or rigidity and satisfactory sealing of the 
plate margin connection are achieved. The plates 2 are connected with one 
another in alternate sequence on opposite plate margins or marginal 
strips, respectively, so that there arise flow-through passages of a 
cross-flow exchanger pack, which passages cross one another in alternate 
sequence. The struts 5 of the frame housing are provided on their side 
facing the edge of the exchanger pack 1 with a triangular recess 9. The 
opposite pack edge with the corner notches 6 of the plates 2 projects into 
the recess 9 of a strut 5. The depth of the recess 9 is dimensioned 
greater than the depth of the corner notches 6, as FIG. 3 shows. The 
recess 9 is sealed or filled by casting with a sealing filling 10 made of 
a moulding resin, preferably a quick-setting synthetic plastics moulding 
resin material. Since the depth of the recess 9 is greater than the depth 
of the clipped-out corner portions or notches 6, the recess 9 can be 
filled up with the sealing filler 10 to beyond the corner notches 6. Thus 
the pack edge is connected to the struts 5 absolutely sealed, so that the 
openings of the throughflow passages which openings lie to the left of the 
strut 5 in FIG. 3, for the one medium, are satisfactorily separated and 
sealed off from the openings of the throughflow passages for the other 
medium, which openings lie to the right of the strut 5. The filling by 
casting of the recesses 9 with the moulding resin-sealing filling 10 is 
effected in the production of the heat exchanger preferably in a manner 
such that in the tilted position of the exchanger pack as illustrated in 
FIG. 3, the quick-setting moulding resin is poured from above, as 
indicated by the arrows 11 in FIG. 3, into those intermediate spaces 
between the plates 2, which spaces are closed in FIG. 3 to the bottom left 
and to the bottom right by the foldings 8 of the marginal strips. The 
moulding resin runs out of these intermediate spaces at the corner notches 
6 and fills the recess 9 to beyond the corner notches 6. During the 
pouring of the moulding resin from the top into these intermediate spaces, 
the moulding resin flows along on the inner side of the folds 8, so that 
in this way the gap between the individual plates 2 on the inner side of 
the fold location is also simultaneously filled with the quick-setting 
moulding resin, as represented with the reference character 12 in FIG. 2. 
This is of great advantage, since in this manner no capillary gaps remain 
between the plates 2 at the folds 8, at which gas corrosion phenomena 
could occur in the case of aggressive media.