Note: Descriptions are shown in the official language in which they were submitted.
INDEX 790
SPECIFICATION
ALUMINUM CHARGE AIR COOLER AND METHOD OF MAKING THE SAME
Field of the Invention
This invention relates to heat exchangers, and more
particularly, to aluminum heat exchangers and heat exchangers
that are particularly suited for use as sa-called charge air
coolers in internal combustion engine systems.
Background of the Invention
For any of a variety of reasons, internal combustion
engine systems are experiencing an increase in the use of
turbochargers. As is well-known, a turbocharger includes
a
turbine wheel that is driven by the exhaust gases from the
engine and which in turn drives a rotary compressor. The
rotary compressor compresses combustion air prior to its
admission to the combustion chambers of the internal
combustion engine. Systems of this sort recover part of the
waste energy that results when incompletely spent exhaust
gases are permitted to expand without performing work and also
provide for higher compression ratios than are attained by the
geametry of the iii4e~na1 combustion engine itself.
It has long been observed that when the incoming
combusta:on air is compressed by the turbocharger
it is
,
simultaneously heated which in turn means that its density is
decreased. Consequently, at any given pressure, a unit volume
of hot air from a tu~booharger contains a lesser quantity of
~axygen available for combustion than would an identical volume
~5 of cold fir at the same pressure. This factor in turn places
a limitat~or~ on the amount c~f fuel that may be burned in
any
given operating aycl~ of an in~e~~nal combustion engine, which
in turf lianits the output thereof. Consequently, particularly
in veYzicular applications, a so-called charge air c~oJ.er has
3o been introduced between compressor stages or between the
compressor side of the turbocharger and the intake manifold
(or equivalent) for the internal combustion engine. The hot,
~gmbust~.oz~ air from the turbocharger is passed through the
charge air cooler to the engine. At the same time, ambient
INDEX 790
air is being passed through the charge air cooler in a flow
path isolated from the combustion air, taut in heat exchange
relation therewith. Consequently, cooling of the combustion
air is obtained to increase the density of the combustion air
to ultimately provide a greater quantity of oxygen per charge
of air to the engine to support combustion.
It can readily be appreciated that even though the
elevated pressure of the combustion air results in a
relatively small pressure differential with ambient, charge
air coolers operate in relatively stressful environments.
Typically, because they arc employed in vehicular
installations, they are subject to a great deal of vibration
and shack as the vehicle travels over the underlying terrain.
Furthermore, they are subject to thermal cycling,
that is, alternating heating and cooling, not only as the
vehicle engine is turned on or off; hn~t. dt_,ring operation of
i the same at varying speeds. Changes of combustion air
velocity with varying engine speed within the tanks of a
'' typical charge air cooler may result in temperature gradients
as high as 25 ° F from one tube to the next which, over a period
of time, can result in substantial stress at tube to header
j pints .
Finally, even though as mentioned previously,
typical charge air coolers do not operate at
pressure
significantly above ambient, because charge air coolers arc
required to pass a large volume of combustion air to the
engine with minimal resistance, large flow paths are employed,
which in turn are defined by surfaces of a relatively large
area. And where even extremely low pressure differentials are
applf~d across large surface areas, those skilled in the art
will appreciate that substantial foroes exist, thus putting
further stress on charge air cooler components.
The present invention is directed to overcoming one
ar more of the above problems.
Summ~ry of the Invention
It is the p~°inc~.pal obj ect of the invention tc
provide a r~ew and improved heat exchanger. More specifically ,
it is an object of the invention to provide a new and improved
INDEx 790
heat exchanger that is specifically intended to be utilized as
a oharc~e air cooler along with a method of manufacturing the
same.
According to one facet of the invention, the
foregoing object is achieved in a method of making a heat
exchanger which includes the steps of: (a) providing a fin
and tube bundle of spaced, parallel tubes and interposed fins
with braze clad material at the interface of the tubes and
fins; (b) providing a metallic channel with braze clad
material on both sides thereof; (c) forming in the web of the
channel a series of apertures shaped as the cross section of
the 'tubes and spaced according to the nominal spacing of the
tubes and with peripheral flanges extending from the web i
n
the da.rection of the legs of the channel to thereby define
a
header plate; (d) assembling the header and the fin and tube
bundle together with the tubes entering respective 4
t
pei
urcs
and located within the associated flanges; (e) ass
bli
em
ng a
metallic tank to the header opposite of the bundle; and (f)
subject~.ng the assembly resulting from step (e) to brazing
conditions sufficient to braze the fins to the tubes
th
,
e
tubs to the flanges and the header to the tank.
In a preferred embodiment, the header channel, the
tubes and the tank are farmed primarily of aluminum.
In a highly preferred embodiment, step (c) is
performed by first forming spaced h6~es in the web of a sid
e
less than the cross section of the tubes and then driving a
punch having a cross section like that of the tubes through
the holes to create the apertures and the associated flanges.
The invention further contemplates that the tubes be
flattened tubes and that the apertures be elongated and
extend
between the legs of the channel
In thi
.
s embodiment, the
fla~g~er., at the ends of the apertures, are in substantial
abutment with the legs. This allows a maximum depth of the
head exchanger c~re for any given tank size.
The invention also contemplates that the step of
driving the punch include forming a concave cam surface at
least partially about each aperture on the side thereof
opposite the flanges to provide a pilot surface for caroming
a c;,r
~J H°'1
l~~ ~ ~ r. ~u:
zrrDEx X90
the tubes into their respective apertures during the
performance of step (d).
According to another facet of the invention, there
is provided a method of making a heat exchanger which includes
the steps of (a) providing a fin and tube bundle of spaced
tubes and interposed fins; (b) providing a channel having a
web and spaced legs; (c) forming a header plate by forming in
the web of the channel a series of apertures shaped as the
cross section of the tubes and spaced according to the nominal
spacing of the tubes and with peripheral flanges extending
from the web in the direction of the legs of the channel and
further forming a concave cam surface at least partially
around each aperture on the side thereof opposite the flange
to provide a pilot surface for caroming a tube into the
associated aperture; (d) abutting the header plate resulting
from step (c) to the bundle and relatively moving the two
toward each other so that tubes enter their respective
apertures with or without piloting by initial contact with the
concave cam surfaces; (e) fitting a tank between the legs of
the channel; and (f) bonding the tubes and the tank to the
channel.
Zn a preferred embodiment of the invention
immediately preceding step (f") is performed by brazing.
The invention also contemplates the provision of a
heat exchanger which includes first arid second spaced,
elongated, opposed tanks each having a heat exchange fluid
port and a header plate receiving opening. A pair of header
plates are provided, one for each tank and each is defined by
an elongated channel having flat, central web flanked by
space, generally parallel legs. The legs of each header plate
flank corresponding sides of the header plate receiving
opening of the associate: tank and are sealingly bonded
thereto. The web of each header plate includes a plurality of
spiced, elangated apertures extending substantially from leg
to leg. Each aperture, on the same side of the web as the
legs, has a peripheral flange with that part of the flange at
the ends of the aperture being in substantial contact with the
associated leg, Each aperture further includes, on the side
of the web opposite the flange, a concave pilot surface at
y ~?a
INDEX 790
- 5 -
least partially surrounding the aperture for piloting a tube
into the associated aperture. A plurality of spaced,
parallel, flattened tubes extended between the tanks and have
their ends in aligned ones of the apertures in opposite ones
of the pair of header plates. Fins extended between and abut
the tubes.
In a highly preferred embodiment, the heat exchanger
is a charge air cooler for use with an internal combustion
engine. Each of the tanks tapers away from the associated
heat exchanger fluid part to a progressively smaller cross
section and serpentine fins are interposed between and bonded
to adjacent ones of the tubes,
In a highly preferred embodiment, the header plate
is aluminum and braze clad on both sides thereof. The
interior of the flange about each aperture is farmed of one of
the sides of the header plate and thus carries braze clad.
The tubes are formed of aluminum and brazed to the headers by
the braze clad material from the one side located an the
interior of the flanges. The facing sides of the legs else
include braze clad from the other side of the header tank and
the tanks axe aluminum and brazed to the header plates by the
braze clad on the other sides of the header plates.
Other objects and advantages will become apparent
from the following specification taken in connection with the
accompanying drawings.
Description of Drawincts
Fig. 1 is a side elevation of a heat exchanger,
Specifically a charge air cooler, made according to the
invention and which is also virtually identical in appearance
to a prior art charge air cooler;
Fig. ~ is a fragmentary, perspective view of a
header plate made according to the prior art;
Fig. 3 is a view similar to Fig. 2, but illustrating
a header plate of mare recent vintage, though still prior art;
Fig. 4 is a view similar to Figs. 2 and 3, but of a
f
header plate made according to the invention;
Fig. 5 is a sectional view taken approximately along
the line 5-5 in Fig. 4;
~~'a~~~~;~
INDEX 790
- 6 -
Fig. 6 is a sectional view taken approximately along
the line 6-6 in Fig, e~;
Fig. 7 is a sectional view taken approximately along
the line 7-7 in Fig. 4;
Fig~ 8 is a fragmentary, bottom view of the header;
Fig. 9 is a fragmentary, plan view of the header at
an intermediate state in its construction;
Fig. 10 is a perspective view of a die or fixture
that may be utilized in forming the header;
Fig. 11 is an elevation of a punch that is used with
the die of Fig. 10;
Fig. 12 is an elevation of the punch taken at 90 ° to
Fig. 11: and
Fig. Z3 is a block diagram illustrating steps in a
method of manufacturing a heat exchanger according to the
inventx.on.
Descri Lion of the Preferred Embodiment and of Prior Art
Header Plates
An exemplary embodiment of a heat exchanger made
according to the invention is illustrated in Fig. 1 in the
fog of a charge air cooler. However, it is to be understood
that the advantages of the invention may be advantageously
employed in heat exchangers intended for use other than as
charge air coolers and 'that no restriction to charge air
coolers is intended except to the extent set forth in the
claims hereof. At the outset, it should also be observed that
the charge air cooler shown in Fig. 1 is conventional except
insofar as the header plates of the same are concerned. With
'that background, Fig. l will now be described.
Op The charge air cooler includes opposed tanks l0 and
~.2 which preferably are formed of aluminum. The tanks 10 and
12 have respective rectangular openings 1~ and 15 which extend
substantially, but not entirely, the length of the respective
tank ~:0 or 12.
35 .fit them upper ends, the tanks 10 and 12 include
heat exchange fluid ports l8 and 20 respectively which extend
rearwardly as viewed in Fig: 1. one of the ports 18, 20 may
be connected to the outlet of a turbocharger forming part of
~~"~'~~~'~ ~
INDEx 790
- 7 _
an internal combustion engine system while the other of the
ports :18, 20 is ultimately connected to the intake side of an
internal combustion engine, both in manners well-known in the
art.
To minimize weight and yet provide adequate flow
area for good flow distribution, each of the tanks 10, 12 is
tapered as at 22, 24 as one progresses away from the
associated port 18, 20. Thus, the cross section of the
interior of each of the tanks 10 and 12 progressively is
reduced as the distance from the port 18, 20 increases.
The openings 14, 16 in the tanks l0 and 12 are
completely covered by channel shaped header plate 26, 28 which
may be identical to one another. Consequently, in the ensuing
description, onJ.y one will be described.
Extending between the header plates 26 and 28 is a
fin and tube bundle, generally designated 30. The bundle 30
is made up of three components, namely, side plates or pieces
32 and 34 at the top and bottom of the bundle 30, parallel,
elongated, flattened tubes 36 extending between the headers
26, 28 and entering the associated tanks 10, 12 to be in fluid
communication with the interior thereof, and serpentine fins
38 located between adjacent tubes 36 or one of the tubes 36
and an adjacent side plate 32, 34. It will be observed from
Eig. 1 that the side plates 32, 34r-while elongated, have a
length less than the distance betweei~ the headers 26, 28.
At this point, a pause in the description of the
preferred embodiment of the invention is considered in order
fox the purpose of discussing prior art header constructions.
As mentioned previously, the headers 26, 28 are formed of
channels and to that extent are no different than the prior
art such as the prior art header, generally designated 40,
shown ~.n Fig. 2. Th4 header 4o includes a flat, central web
42 and two, generally parallel legs 44, 46 flanking the same.
~~~h~~ the Web a~'e a series of elongated apertures 48 which
are spaced apart a distance corresponding to the nominal
spacing between the tubes 36 and which are elongated in the
direCti°n extending between the legs 44 and 46. The length of
the elongation o~ the apertures 48 is equal to the length of
elongation of the Cross section Of each of the tubes 36. It
INDEX 790
g _
will be observed that in the prior art header 40, the ends
5 of the apertures 48 stop short of extending all the way
to the
inner surfaces of the legs 44 and 46 which are represented
by
dotted lines 52 and 54 respectively. In the usual case,
the
tubes 36 would be brazed within the apertures 50.
In use as part of a charge air cooler, the header 40
would be subjected, on its suxface between the legs 44
and 46,
0 to varying pressures and it will be immediately appreciated
that the structure is such that the areas of the web 42
surrounding each aperture 48 will flex much like a diaphragm
in response to pressure changes within an associated tank
or 12. As a consequence, the tube to header joints wars
subject to such flexure and would be prone to fail as a
result
of stress and fatigue.
Recognizing this problem, the prior art turned to a
header construction as shown in Fig. 3 and generally
designated 60. In this case, there is again a flat central
web 62 flanked by parallel legs 64 and 66. Apertures 68
that
are elongated and shaped to receive the tubes 36 extend
between the legs 64 and 66. However, in this case, the
ends
5 70 of the apertures extend substantially to the inner surfaces
of each of the legs 64, 66 as indicated by dotted lines
72, 74
respectively. That is to say, the area of the web 42 existing
between the end 50 of each of the apertures 48 and the
inner
surface 52 or 54 of the adjacent leg 44 or 46 is eliminated
in
"the prior art -structure of Fig. 3 which in turn greatly
reduces or eliminates all together the diaphragm flexing
effect found in the prior art structure of Fig, 2,
However, the prior art structure of Fig. 3 continues
30 to share other difficulties found in the embodiment of
Fig. 2.
For example, rigidity across the web 62 is less than desired.
For another, in order to braze aluminum tubes into the
5 apertures 68 or the apertures 48, braze metal would either
have tca flow from the surface of the web 62 or 42 ~~around
the
corncrib into the apertures 68 or 48 or else the tubas
themselves would have to be braze clad. In the case of
the
former, a higher pexcentage of imperfectly formed or weak
joints i~ encountered while in the case of the latter,
providing all of the tubes with braze clad along their
entire
zrrnEx 790
_9_
lengths essentially only to use the braze clad at the ends
thereof is undesirably expensive.
Still a further problem in terms of difficulty of
assembly was encountered. Tn the usual case, the fin and tube
bundle 30 are formed and placed in a fixture. Header plates
are located at apposite ends thereof and nominally aligned
with the ends of the tubes 36. Lateral pressure is exerted on
one or both of the side plates 32, 34 toward the other side
plate while providing relative movement of the header plate
26, 28 toward the associated ends of the tubes 36. The
pressure is intended to be sufficient to compress the bundle
30 to cause alignment of the tube ends 36 so that they could
readily enter the apertures 48 or 68 and the webs 42 or 62,
respectively. This process, however, is somewhat tedious and
if attempts are made to speed it up by enlarging the apertures
48, 68 so they will more readily receive the ends of the tubes
36, there results an increase in the tendency to improperly
form a tube to header joint in the subsequent brazing process.
With the foregoing in mind, the improved header 26,
28 of the invention will be described and inasmuch, as noted
prev.~ouslY. as the, two are identical, only the header 26 will
b~ described. Referring to Figs. 4 -~ 8, the header 26 is seen
to be formed of a central, flat web 80 flanked by parallel,
elongated legs 82, 84. Typically, the header 26 will be made
og aluminum and in addition, will be provided with braze clad
material clad on both sides thereof.
Elongated apertures 86 are boated in the web 80 and
extend between the legs 82, 84. As seen in Figs. 5 and 6, the
periphery of each of the apertures 86 is completely surrounded
bY a flange 88, 90, 92, 94 located between the legs 82, 84.
As can be ascertained from Fig. 5, the flange 88, 90, 92, 94
includes trio elongated f~.ange sides 88 and 90 and as can be
seen in Fig. 6, the flange sides 88 and 90 terminate in
rounded end flanges 92 and 94 which as seen in Fig. 8 define
a cont~.nuous single flange 88, 90, 92, 94 with the end flanges
92, 94 of such flange being in substantial abutment with the
adjacent leg 82, 84. This provides apertures 86 having a
length that minimizes or eliminates the diaphragm effect just
INDEX 790
- 10 -
as the apertures 68. Furthermore, by elongating the apertures
86 to the point where the flange sections 92, 94 abut the
corresponding leg 82, 84, for any given tank and/or header
size, core depth is maximized. In most cases this will
increase efficiency without increasing core facial area. In
addition the flange sections 88 and 90, being substantially at
right angles to the plane of the web 80, serve to rigidify the
same from one side to the other to provide enhanced across the
web rigidity over the prior art headers 40 and 60 shown in
Figs. 2 and 3 respectively.
In addition to the provision of the flange 88, gpr
g2, 94 surrounding each of the apertures 86, on the side of
the web 80 opposite the legs 82, 86, each of the apertures 86
is at least partially surrounded by a concave cam surface
having elongated parts 96 and end parts 98 along the length
and at the ends of each of the apertures 86 respectively. it
w~.ll be appreciated that the cam surfaces 96, 98 are on the
tube receiving side of the header 86 and thus when the header
and tubes are moved relatively toward each other, misaligned
tubes will strike the cam surface and be rammed into alignment
and into the apertures 86 so that they may ultimately engage
the inner surface 100 of the flange 88, 90, 92, 94. This
inner surfa,:a 100 is configured so as to fairly closely mimic
the exterior shade of the end of the tube 36 sufficiently that
an excellent braze connection can be achieved.
The manner in which the header 26 is formed is best
understood from a consideration of Figs. 9 - 12. The channel
may be formed by stamping of any sheet of aluminum that is
braze clad ors both sides and elongated holes 110 are disposed
in the web 80 on the centers of the apertures 86 that are
ultimately to be formed therein. ~S Can be seen in Fig, g,
tie holes 110 re narrower than the apertures 86 and have a
lesser, across the web length than the apertures 86.
This channel may then be planed in a fixture or die
111 such as illustrated in Fig. 10. The fixture shown in Fig.
10 includes parallel slots 112, 114 for receipt of the legs
82, 84 respectively. If desired, the upper surface of the
fixture x.11 may incline a pilot proj action 116 that may be
INDEX 790
11 -
received in an endmost one of the holes 110 to properly locate
the channel in the fixture 111.
Cross slots 118 are located in the upper surface of
the fixture 111 on centers corresponding to the centers of the
apertures 86 ultimately to be formed. At the end of each of
the slots 118, on the opposite side of the parallel slot 112
or 114, there is formed a relief 120. The reliefs 120 have a
width approximately egual to the width of each of the slots
O 118, but their depth is only approximately one-half the depth
of each of the parallel slots 112, 114.
Also used in forming the apertures 86 is a punch
such as the punch generally designated 122 in Figs, 11 and 12.
The punch includes an end 124 including a central flat section
5 126 and which is flanked on all four sides by a bevel 128.
The bevel 128 merges into a punch section 130 which has a
configuration or shape that is identical to the interior
surface 100 of the flange 88, 90, 92, 94. The section 130 in
turn merges into a slightly concave bevel or internal round
0 132 which conforms in shape to the cam surface 96, 98. The
round 132 then merges into 'the remainder of the punch 134.
Keeping in mind that the holes 110 are smaller than
the apertures 86, when the channel is arranged in the fixture
111 and the punch applied to the holes 110, it will be
5 appreciated that that material surrounding each of the holes
110, but within the envelope of the ~Znching section 130 will
~efo~ to form the flange 88, 90, 92, 94. Driving the punch
122 fully into the slots 118 will also result in the round 132
coming in contact with the upper surface of the web 80 to
p result in the formation of the concave cam surface 96, 98
surrounding each of the apertures 86. Typically, punches 122
will be gauged so that several or all of the flanges 88, 90,
92, 94 in a single header plate w.il be formed simultaneously.
In practice, it has been found that the formation of
the flange 88, 90, 92, 94 in this fashion results in the
35 exertion of substantial outward force in the area of the
portaona 92 and 94 0~ the flange such that, as seen in Fig. 8,
the outer surfaces of the legs 82 and 84 are slightly bulged
as at 140. However, these bulges are directed into the
~~~~G.'~~.~.
INDEX 790
- 12 -
reliefs 120 in the fixture 111 and as a consequence, any
tendency of the header to wedge within the fixture 111 is
avoided.
Fig. 13 illustrates, in block form, a method of
manufacturing a heat exchanger such as a charge air cooler,
according to the invention. Blocks 140 and 142 implement
steps in the formation of the headers as described immediately
preceding. That is, they illustrate the steps of providing an
aluminum channel with both sides braze clad and with a web
that is initially slotted as well as the formation of
peripheral flanges on the slots by punching to define the
header plate. Another initial step in the invention is
illustrated at a block 144 and is the step of providing the
fin and tube bundle 30 including the side pieces 32, 34, the
tubes 36 and serpentine fins 38 between the tubes 36 or
between a tube 36 and one of the side pieces 32 and 34. This
is done in a conventional fashion by alternately stacking the
tubes and the fins and then utilizing any suitable fixture to
maintain the same in assembled relation.
2 0 In the usual case, the tubes 3 6 will be aluminum and
the fins 38 aluminum as well. Usually, but not always, the
tubes 36 will be extruded. Typically, the fins will be formed
of aluminum brazing sheet to provide the braze metal required
to bond to the tubes 36 and the side pieces 32 and 34.
Also, in the usual case, the tubes 36 will
previously have been provided with internal turbulators as,
for example, lanced and offset turbulators. When such
turbulators are provided, the tubes are frequently "spanked"
to abut the turbulators preliminary to a brazing operation.
At the block designated 146, the headers 26 and 28
ax°e assembled to the fin and tube bundle 30. This is
acc~smpli~laed by effecting relative movement between the fin
and tube bundle 30 and one of the headers 26 such that the two
move toward each other. Those ones of the ends of the tubes
36 that are perfectly aligned with a corresponding aperture 86
will, of course, enter such an aperture without difficulty.
Those that are anisaligned, will encounter the cam surfaces 96,
98 and be piloted into the corresponding aperture 86. The
tube ends are caused to enter the apertures 86 at least to the
~' a'~:~ ~ ~
1NDE~ 790
- 13
depth of the flange 88, 90, 92, 94. A fixture may be used tc
maintain the headers 26, 28 assembled to the fin and tube
bundles 30 as is well-known.
The next step is to assemble the tanks 10 and 12 and
the headers 26, 28, respectively; and such a step is
illustrated in the block 148, As can be seen in Fig. 1, the
tanks 1~, 12 are nestled between the legs 84, 86 of the
respective header 26, 28 and orientated such 'that the entire
header receiving opening 14, 16 is covered. Again, a suitable
ZO fixture may be utilized to maintain the tanks 10 assembled to
the headers.
Thereafter follows a brazing operation such as
illustrated at the block 150. The brazing operation involves
exposing the tank-header-fin and tube bundle to brazing
conditions for a sufficient period of time as to cause the
f~.ns 38 to braze to the tubes 36, the tube ends to braze to
the flanges 88, 90, 92 , 94, the legs 82, 84 to braze to the
tanks 10, 12 and for the side of the web 80 between the legs
82, 84; at the ends thereof, to braze to the tanks Z0, 12
adjacent the ends of the openings 14, 16.
Once the brazing operation has been completed, the
fixtures may be removed as indicated by a block 152.
~s alluded to earlier, substantial advantages flow
from tie invention. For one, the provision of the cam
surfaces 96, 98 surrounding each of the apertures 86 eases
assembly in terms of providing a ready means for the ends of
he tubs 36 to enter the apertures 86. The provision of the
flange 88, 90, 92; 94 around each of the apertures 86 provides
two advantages. For one, it rigidifies the web 80 in the
across the web direction. Fox another, because it is formed
:~~ the manner previously described out of aluminum sheet which
is braze clad on both sides, it will be readily appreciated
that the inner surface 100 of the flange 88, 90, 92, 94
remains provided with the braze clad material to provide an
excellent bond, That is to say, the brazed tube t~ header
joint does not req~~,re the flow of braze clad material from
some ether location on the header nor does it require t3ae use
of ~ra~e cladding on the tubes 36. And where the flange
sections 92, 94 abut the legs of the channel, core depth is
~C~'~~~~~
IDTDE~ 790
- 14 -
maximized for improved efficiency. Alternatively, for any
given core, header depth may be reduced to thereby minimize
the volume of the heat exchanger.
At the same time, the braze clad on the opposite
surface of the sheet of which the header 26 is formed provides
braze clad material on the inner surfaces of the legs 82 and
84 to provide a braze and sealed joint along those legs with
the respective one of the tanks 10, 12. The braze clad
material on the same side of the original sheet, but on the
underside of the web 80 also acts to provide a brazed and
sealed joint at each end of the header 26 or 28 to the tank
10, 12.
Thus, the invention provides not only an improved
method of fabricating a heat exchanger such as might be used
as a charge air cooler, but an improved heat exchanger which
is ideally suited for use in the hostile environment
encountered by a charge air cooler employed on a vehicle.
