Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
2060247
Background of the Invention
This invention relates to heat exchangers and, more
particularly to motor vehicle heat exchangers or
radiators and to a method of joining the members thereof.
Users of heat exchangers, particularly those used in
automotive and truck engine-cooling radiators, are
interested in achieving longer life in units which they
l0 purchase. Truck manufacturers are especially seeking a
longer life radiator which can withstand the extra stress
and abuse in a truck environment for significantly longer
mileage.
The joints between the tubes and headers in heat
exchangers in general, and automotive type radiators in
particular, have received increased scrutiny in the goal
to achieve longer service life. Typically, the
tube-to-header joint had been a simple tin/lead soldered
joint between a thin walled brass tube and a thicker
header which has a collared hole to receive the tube.
Because of expansion and contractian of the tube during
the heating and cooling cycle present in operation, the
joints between the tubes and the headers are placed in
shear stress. Shock and vibration in the motor vehicle
environment add to this stress. In addition, chemical
reactions between the coolant and any solder_which covers
the header surface on its water side can cause corrosion
products which can flake off and clog the radiator tubes,
thereby leading to engine overheating.
2osoz47
-2-
Welding has been used to bond the tube-to-header
joint in order to strengthen this portion c~f automotive
radiators. However, current methods of welding do not
provide a completely leak-free welded joint in every
instance. w To rectify this problem, it has been a
practice to apply a caating of solder on the air side of
all of the joints to seal any leaks in the weld area
between the tube and header. This operatimn requires the
placement of expensive perforated solder foil or other
prefabricated forms of solder over the tubes on the
radiator core prior to assembly of the header to the
core. After welding the tubes to the header collars, the
header is then dipped in flux and must be heated
extensively to cause the solder foil to melt and form the
sealant coating on the air side of the header. During
this operation, solder. flows through the usually numerous
tube-to-header joint leaks and considerable solder
appears on the water side of the header. This operation
is energy intensive, time consuming, and often causes the
header to warp due to the high temperatures in the
heating operation. Also, the core must normally still be
tested to determine the integrity of the tube-to-header
joints. In spite of the air-side solder coating, there
may often appear several joints which remain unsealed and
leak coolant fluid. These joints must then be repaired,
usually by hand methods such as using a torch and wire
solder on the air side of the joint.
In order to attempt to achieve leak-free
tube-to-header joints, resizing of the radiator core
tubes has been performed prior to and/or after attachment
of the header. U.S. Patent Nos. 4,744,505 and 4,858,686
disclose a method of resizing the ends of oval or
~r ~ ~ ~ ~
-3-
non-circular header tubes to a circular shape, inserting
the ends of the tubes into circular collar openings
having a slightly larger diameter, and thereafter
expanding the outermost portion of the tube ends to
create a tight fit with the collar opening. However,
even with such resizing, the subsequent welding of the
joints still does not usually produce a leak-free joint
and, consequently, solder is used to seal the welds.
Furthermore, the many steps involved in resizing are time
consuming and require positioning and handling of the
heavy and unwieldy core. This adds to the cost of
manufacture, and the difficulty of the operations
contributes to wide variations in product quality.
Alternative methods of sealing the tube-to-header
joints include applying flux to the liquid side of the
banded joint and then applying a coating of solder, for
example, by dipping into a bath of molten solder or by
the use of ware soldering techniques. These methods
result in lower header temperatures and thereby minimize
warping and the need for repair. However, the increased
amount of solder left on the water side surface of the
header creates a potential for the creation of solder
corrosion products, also termed "'solder bloom".
Bearing in mind the problems and deficiencies of the
prior art, it is therefore an object of the present
invention to provide an improved tube-to-header joint for
use in heat exchangers and, in particular, automotive
type radiators.
It is another object of the present invention to
provide a heat exchanger in which the tube-to-header heat
exchanger joints are substantially leak-free.
2060?4~
-4-
It is a further object of the present invention to
provide a tube-to-header heat exchanger joint which
minimizes the need for post-production testing and repair
for leaks.
It is another object of the present invention to
provide a method of manufacturing a tube-to-header heat
exchanger joint which minimizes complicated, time
consuming and unwieldy handling of the heat exchanger.
It is a further object of the present invention to
provide a method of manufacturing a tube-to-header heat
exchanger joint which avoids resizing of tube ends after
the core assembly is fitted to the header.
It is yet another object of the present invention to
provide a tube-to-header heat exchanger joint which
minimizes the amount of solder in contact with the heat
exchanger liquid.
It is a further object of the present invention to
provide a solder sealed tube-to-header heat exchanger
joint which reduces the total amount of solder used,
utilizes less expensive solder, and minimizes the effort
needed to apply the solder during the production of the
heat exchanger.
It is another object of the present invention to
provide a welded solder sealed tube-to-header heat
exchanger joint which can be readily manufactured by
mass-production techniques and which results in an
improved product.
~U~O?4~
-5-
The above and other objects, which will be apparent
to those skilled in the art, are achieved in the present
invention which provides a method of affixing a plurality
of tubes to a plurality of corresponding openings in the
header wall of a heat exchanger in which the wall has an
inner, liquid-facing side and an outer, air-facing
side. In one aspect of the invention directed to
insertion of the tubes into the header openings, the ends
of oval tubes are sized such that the minor diameter of
the tube ends is greater than the minor diameter of the
header openings and the major diameter of the tube ends
is less than the major diameter of the header openings,
with the circumference of the tube ends and the header
openings being substantially equal. The tube ends are
inserted into corresponding openings in said header wall
whereupon the minor diameter of the tube ends is reduced
and the major diameter of the tube ends is increased to
create a substantially fully contacting fit around the
circumference with said header openings. The tube ends
are bonded to corresponding openings in the header wall
to form a plurality of welded tube-to-header joints on
the heat exchanger.
In bonding the~tubes and header openings, the tube
ends are welded to corresponding openings in the header
wall, such that the tubes extend toward the air-facing
side of the wall, to form a plurality of welded
tube-to-header joints. In this aspect, non-circular
tubes, for example oval shaped, can be utilized.
NO~~?4'~
-6-
Flux is then applied to the air-facing side of the
tube-to header joints, and thereafter a lead/tin or other
solder is applied to the liquid-facing side of the
tube-to-header joint to flow the solder into any voids in
the welded joints and substantially seal the joints
against leakage of liquid. Only those joints having
potential liquid leaking voids receive the solder.
Sound, liquid-tight welded joints are not solder sealed.
Preferably, the method of sizing the tube ends to an
oval configuration is used in conjunction with the
aforementioned method of welding and soldering the
tube-to-header joint. Also, the openings in the header
wall preferably comprise collars drawn or formed from the
header wall. Flux may be sprayed onto the air-facing
side of the tube-to-header joint and thereafter the
molten solder may be applied either by dipping the liquid
facing side of the joint into a bath of molten solder or
passing itwthrough a molten solder wave. In further
aspects, the invention comprises heat exchangers having
tube-to-header joints produced according to the
aforementioned methods. Following solidification of the
solder, the liquid-facing side of the tube-to-header
joints should be substantially free of solder to minimize
corrosion products inside the heat exchanger during use.
ref Description of the Drawincxs
Fig. 1 is a side elevational view of the core
assembly of a heat exchanger, made up of the tubes and
fins (partially cut away), attached to header plates
prior to bonding of the tube-to-header joints in
acc~rdance with the method of the present invention.
'060247
Fig. 2 is a close up cross-sectional view of a pair
of tubes inserted into openings in the header wall of the
heat exchanger depicted in Fig. 1.
Fig. 3a is an axial cross-sectional view of an
undeflected oval tube end, perpendicular to the axis of
the tube, as it is sized prior to insertion into the
header plate.
Fig. 3b is an axial cross-sectional view of an oval
shaped, collared header opening prior to insertion of a
tube.
Fig. 4 is an axial view of the cross-sectional view
of the tube end of Fig. 3a superimposed upon and over the
cross-sectional view of the collared header plate opening
of Fig. 3b.
Fig. 5 is an axial cross-sectional view of the tube
end of Fig. 3a after insertion into the header plate
opening of Fig. 3b.
Fig. 6 is a side elevational view of the
cross-section ,of a pair of tube-to-header joints on a
heat exchanger header wall during the application of flux
in accordance with the method of the present invention.
Fig. 7 is an axial cross-sectional view of the end of
a heat exchanger tube depicted in Fig. 6.
Fig. 8 is a side elevational close up view of a
cross-section of a welded tube-to-header joint having
weld voids.
Fig. 9 is a side elevational view showing a heat
exchanger (illustrating two different types of fins
partially cut away) during the solder application step in
accordance with the method of the present invention.
Fig. 10 is a cross-sectional view of tube-to-header
joints produced in accordance with the method of the
present invention.
~060?47
_8_
Detait_ed pescripti~~ of the Invgnti~r,
Reference will be made herein to Figs. 1 to 10 which
detail various portions of the method and article of the
present invention.. Unless otherwise specified, the
materials used to construct the heat exchanger can be any
conventional material for such use, such as aluminum,
brass or the Like. Like numerals refer to like features
of the invention throughout the drawings.
Initially, the heat exchanger core components are
prepared. These include conventional heat exchanger
tubing, for example solder coated brass tubes, and
conventional copper heat transfer fins. In the preferred
embodiment of the invention, stackable serpentine or
similar type fins are employed along with, for example,
terne plated core side pieces and solder foil strips for
bonding of the core side pieces to the core. Header
plates having openings conforming to the size and shape
of the tube ends are also prepared. Preferably, the
header openings which are to receive the tube ends are
prepared by drawing the openings to form a collar
extending outward from the header plate.
In accordance with a first aspect of the method of
the present invention, there are preferably utilized
tubes having oval ends sized in a particular manner in
relation to oval openings in the header plate. As used
herein, the term oval" refers to any non-circular shaped
axial cross-section (i.e., perpendicular to the axis of
the tube) having a generally smoothly curving periphery,
such as an ellipse a rectangle with rounded corners, or
other obround or egg shape. Being of oval
20~~?47
_g_
cross-sectional shape, such tubes ends will have a
diameter in one direction greater than the diameter in
another (usually perpendicular) direction, which are
referred to herein as the "'major diameter" and "'minor
diameter"', respectively. It has been found that use of a
special configuration of the oval cross-sectional shapes
of both the tube ends and header plate openings requires
fewer steps for manufacture and results in improved
quality of the welded joints and reduction in the amount
of solder required for sealing of the wells. This is
accomplished by either, sizing or resizing each of the
individual core tubes on both ends so that the minor
diameter of the outside of the tube ends is greater than
the minor diameter of the opening in the header plate and
the major diameter of the outside of the tube ends is
less than the major diameter of the opening in the header
plate. The circumferences of the outside of the tube
ends and the opening in the header plate are
substantially equal. For the preferred embodiment which
employs stackable tube and fin components, such as oval
or obround cross section tubes and serpentine type fins,
the ends of the core tubes are sized or resized prior to
assembly of the core components. This sizing may be
accomplished in an automated operation by inserting an
appropriately shaped flaring tool to form the oval tube
end configuration as described above.
The aforementioned heat exchanger core components are
then assembled by stacking the tubes, serpentine or
similar type fins, and side plates to form a core block
assembly. When the header plate is thereafter pressed
onto the core assembly such that the oval tube ends are
inserted and fitted into the corresponding header
2~i~'4~N47
-1~-
openings, the walls of the tube ends deflect and deform
such that the minor diameter decreases while the major
diameter increases to meet the same dimensions as the
header plate opening, thereby creating a fully contacting
tight fit in the tube-to-header joint. The selection of
tube and collar dimensions is made to provide this fully
contacting tight fit with a minimum of force required to
press the header onto and over the tube ends.
After the header plate is attached over the tube ends
of the core assembly, the core is then baked with the
headers in place, eliminating the need for false header
fixtures. This baking results in soldering of the core
components. After baking, the core is ready for
tube-to-header joint welding with no further resizing or
flaring of the tube ends. The resulting welds are of
generally uniform high quality because of the good
tube-to-header fit. Other methods of bonding the tubes
to the header openings may also be used, for example, by
soldering. However, the preferred method of bonding the
tube-to-header joints is by welding and soldering as
described further below.
Instead of using the serpentine or similar stackable
type fins, conventional plate type fins may be used in
assembling the heat exchanger core block. With such
fins, the tubes are inserted through tube openings in the
plate type fins, rather than being stacked together with
the tubes during assembly as with the serpentine type
fins. The assembled tube and plate type fin core block
is then baked without the header plates to bond the
components. Because flaring of the tube ends would
interfere with insertion into the openings in the plate
fins, the tube ends should be sized to their oval
?tl~~~~~
-11-
configuration as described above only after the assembly
with the fins and, preferrably, after the baking
process. Following baking, the header plates are then
fitted over the tube ends and bonded thereto. The use of
serpentine o.r similar type stackable fins is preferred
since the oval tube ends may be more easily sized prior
to assembly of the core block, with the result that the
more costly step of sizing the core ends after assembly
and baking is eliminated.
l0 Figs. 1-5 depict the preferred method of assembling
the heat exchanger prior to bonding of the tube-to-header
joints. Referring to Fig. 1, there is shown the
assembled basic components of the heat exchanger 33
fitted together prior to the initial baking operation.
Tubes 10 are arrayed in a typical parallel configuration
and serpentine fins 40a (shown only partially over the
tubes for illustration purposes) are fitted to the tubes
to create a stacked, unbonded core assembly. To assist
in holding the core assembly in place during the baking
cycle and to maintain alignment of the core tubes, header
plates 16 having collared header openings 17 are fitted
to the core assembly by inserting the tube ends into the
collared openings.
The unbonded tube-to-header joint is shown in more
detail in Fig. 2 which depicts a pair of tubes 10 and l0a
as fitted into collared openings 17, 17a of header plate
16. The tubes 10 and l0a have oval tube bodies 12, 12a
with flared oval tube ends 13, 13a, respectively. The
collar openings 17, 17a extend from the water-facing side
16b in a direction opposite the air-facing side 16a of
header plate 16. The tube ends 13, 13a are fitted into
the respective collar opening 17, 17a so that the ends of
2~~~?47
-12-
the tubes and collars are essentially coplanar and the
tube bodies extend from the air-facing side 16a of the
header plate.
An axial cross-sectional view of flared oval tube end
13, transverse or perpendicular to the tube axis prior to
insertion in the header, is depicted in Fig. 3a. The
major diameter of tube end 13 is shown as AT and the
minor diameter is shown as CT. Both the major and
minor diameters are measured at the outside or exterior
of the tube periphery.' The sizing of tube end 13 in
accordance with the method of the present invention
results in the tube end major diameter AT being
somewhat smaller than the major diameter of the oval tube
body 12 and the tube end minor diameter CT being
somewhat greater than the minor diameter of tuba body
12. Fig. 3b depicts a cross-sectional view of header
plate collar opening 17 wherein AB is the major
diameter and CH is the minor diameter. Both the major
and minor diameters are measured at the inner periphery
of collar 17.
Fig. 4 depicts the undeformed tube end 13 as shown in
Fig. 3a superimposed over the collar opening depicted in
Fig. 3b to illustrate that the minor diameter of tube 13
is greater than the minor diameter of collar opening 17
while the major diameter of tube 13 is smaller than the
major diameter of collar 17. The arrows indicate the
direction of deflection of the tube walls upon insertion
into the header opening.
The insertion of the tube end 13 into collar opening
17 is depicted in Fig. 5 to show the deformation of the
tube end so that its major and minor diameters correspond
to those of the collar. Because the circumference of the
zosoz47
-13-
outer periphery of tube end 13 is substantially equal to
the circumference of the inner periphery of collar
opening 17, there is a close fit between the two which
reduces the likelihaod of void formation during
subsequent bonding of the tube-to-header joint. Actual
tube end and collar diameters may be selected to require
a minimum of insertion force.
Figs. 6-10 depict the preferred method of bonding
tube-to-header joints, and in Fig. 6 there is shown a
portion of the heat exchanger made in accordance with
this aspect of the method of the present invention. Heat
exchanger tubes 10 are provided to carry the working
fluid of the heat exchanger to any fins (not shown) and
between opposed headers, a wall of which is shown as 16.
As seen in Fig. 7 in an axial cross-section transverse to
its longitudinal axis, the main body portion of tube l0a
has a generally oval shape 12a, the end portions 14a of
which have been shaped into a substantially circular
cross-section. Optionally, the tube body portions may
have other cross sectional shapes. Preferably, tubes
having oval ends sized in accordance with the previously
described method are fitted into appropriately sized oval
header openings, and may be welded and soldered in
accordance with the same principles used in connection
with the circular ended tubes depicted in Figs. 6-10..
The header wall or plate 16 shown is oriented with
the air-facing side 16a facing upward and the
liquid-facing side 16b facing downward, as seen in Fig.
1. Header wall 16 includes a series of openings in the
form of integral drawn collars or flanges 18
substantially conforming to the shape of tube end
portions 14. As shown in Fig. 6, circular tube end
~0~0247
-14-
portions 14 are received within and extending through
circular collar openings 18 formed in wall 16. The tube
body portions extend away and outward from the joint on
the air side of the header wall. Where the tube ands are
not of oval configuration and sized in accordance with
the methods described previously, they may be optionally
sized after insertion into the collar opening to provide
a tight compression type fit between the tube end and the
collar opening, for example, by the method taught in U.S.
Patent Nos. 4,744,505 and 4,858,686, wherein the tube
ends are substantially coplanar with the ends of collar
18 and the outermost tube end portion is expanded to .form
a tight fit with the lip of the collar.
Following the tube insertion step, the tube ends are
bonded to the header wall collar openings 18 by welding.
This process may be performed by any known method, for
example, by those disclosed in the aforementioned U.S.
Patents or those methods disclosed in U.S. Patent Nos.
4,377,024 and 4,529,034. The finished welded tube-to'
header joints are shown as weld beads 20" and 20"'.
In the course of producing a welded or otherwise
bonded tube-to-header joint, voids may be present which
present the possibility of liquid leakage from the liquid
side of the ,header ,through the joint to the air side of
the header. Typical voids 22 are shown in welded joint
20'°' in the close-up of Fig. 8 wherein the void 22
comprises a narrow opening between the liquid and air
sides of header wall 16. Void 22 is shown as a
channel-like opening here only for purposes of
convenience - such voids may be of numerous other shapes
such as gas pockets formed in a weld bead, cracks formed
upon heating or cooling of the weld bead, or areas in
~0~~?~~
-15-
which the welding or bonding has been incompletely made.
The term 'voids is intended to cover these and other
potential liquid-leaking openings in the joint. In any
event, such voids 22 may or may not be present in every
joint, as shown in Fig. 6 wherein void 22 is present in a
first welded joint 20', but absent from a second welded
joint 20~. It is common that at least a portion of, but
not all, of the welded joints in a motor vehicle type
radiator may contain such voids. The present invention
is directed to a method which results in a completed heat
exchanger in which only those welded joints having voids
are sealed by solder, and those welded joints in which
there are no leak causing voids are not sealed by any
solder.
Referring back to Fig. 6, following the welding of
the tube ends to the header wall, the heat exchanger is
preferably positioned on its end so that the
tube-to-header joints face downward, i.e., the header
wall 16 is usually horizontal and the tube bodies extend
upward and vertically from the tube-to-header joints. A
solder flux type material is shown being sprayed by
nozzles 24 into the upward air side 26 of each
tube-to-header joint. These fluxes may be any type
conventionally used in soldering which are capable of
being applied in the manner contemplated by this
invention. Rach joint in a given heat exchanger is
sprayed with flux in this manner so that in those joints
having voids which present the potential for liquid
leakage, the flux may thoroughly coat the area and flow
downward into the void itself either by gravity or
capillary action, or both. The heat exchanger may also
be tilted slightly during flux application to allow any
(~~~w47
-16-
excess flux to run off without coating the water-facing
side of the header. The usually limited size of the
voids which may be present in any of the tube-to-header
joints also prevents excessive amounts of the flux from
running through or around to the water-facing side of the
header plate.
Subsequently, as illustrated in Fig. 9, the welded
and fluxed tube-to-header joints of the heat exchanger
are subjected to a soldering operation by contacting the
liquid facing side of the tube-to-header joint with
solder, for example, by dipping into molten solder. The
preferred method utilizes a solder wave device 28 which
employs a solder pump 30 to form an upward directed
molten solder wave 32. The header tube assembly 34 is
shown on its end to present the downward facing joints 20
to the molten solder. For illustration purposes, both
serpentine type heat exchanger fins 40a and plate type
heat exchanger fins 40b are shown partially on heat
exchanger tube-array 36. Normally, only one type of fin
is employed in the heat exchanger.
During the soldering process, header tube assembly 34
is moved to the right, as shown by the arrow in Fig. 9,
to present the downward facing joints for contact with
the molten solder wave 32. The ends of the
tube-to-header joints 20 are immersed in the molten
solder only to a degree sufficient to draw the solder up,
by capillary action, through any voids present in those
joints. A solder fillet may be formed on the air side of
any such joints. As practiced by the present invention,
the joints are not exposed to any more heat than is
necessary to apply the molten solder in this fashion.
Furthermore, because of the application method, the
~o~uz4~
-17-
solder employed may be of the relatively inexpensive type
used in such molten solder application devices, and need
not be the more expensive foil or wire type solder
utilized in the prior art. Joints which have no voids or
cracks do not draw up any solder and, consequently, no
solder fillets are formed on either the air or water side
of any sound joints. Following solidification, the only
solder which remains on the water side of the header is
that which actually seals the voids in those
tube-to-header joints that have them. There is
essentially no surface coverage by solder on the water
side of the header wall because fluxing is limited to the
voids only, and therefore the water side of the header
wall (aside from the voids themselves) remains
substantially solder free to prevent excessive solder
bloom corrosion.
Typical completed tube-to-header joints made in
accordance with the present invention are illustrated in
Fig. 10 which shows a pair of tubes 10 and l0a joined to
header wall 16. Tube 10 on the left is secured to the
header wall by welded joint 20' which initially included
a pair of voids 22 through the joint from the liquid to
the air side. As a result of the fluxing and soldering
operation of the present invention, voids 22 have been
sealed by solder which has been drawn up through the
voids by capillary action to seal not only void 22 but
also provide a fillet type seal 38 on the air facing side
of the joint. Because the flux was initially applied to
the air-faa~ng side of this joint, essentially no solder
remains on the liquid side of joint 20'. The other tube
10a is shown as having been initially sealed to header
wall 16 by a sound welded joint 20"' which contained no
~0~0?4'~
-18-
voids which would provide potential points of leakage.
Although the welded joint 20"' also had flux applied an
its air side and contacted with molten solder on its
liquid side during the soldering operation, the soundness
of the joint prevented any flux from passing through to
the liquid side. Thus, joint 20"' is substantially free
of solder on both its air side and liquid side.
Following the solder application step of the present
invention, the manufacture of the heat exchanger may be
continued and completed by bonding the header tanks onto
the respective header walls by any conventional methods
such as those described in the aforementioned U.S.
Patents.
The method of resizing the oval tube ends described
herein significantly reduces the handling of the heat
exchanger during the manufacturing process compared to
prior methods, particularly those which require resizing
of the tube ends after assembly and baking of the core
and again after fitting to the header. Additionally, the
resizing results in a proper, tight fit between the tube
end and header for subsequent bonding. This reduces the
cost of manufacturing and variability in product quality.
The method of applying the flux and solder sealing of
welding joints according to the present invention results
in a welded radiator product which has less solder on the
water side of the header than prior art methods.
Furthermore, the mass-produced heat exchanger which
results from this method is unique in that solder appears
on the water side of the header only where void sealing
is required, and solder appears on the air side of the
header as a fillet around only those tube-to-header
joints which require the sealing of a void. Thus the
~?0~0?~7
-19-
present invention results in welded tube-to-header joints
with greatly increased strength over soldered joints with
the advantage of minimizing the amount of solder in
contact with the coolant and effectively eliminating the
undesirable effects of solder bloom corrosion. The
actual amount of solder coating is limited to the
location of actual leaks and is only a fraction of the
amount of solder employed in a solder dipped header.
This amount of solder is considerably less than the
amount created on prior art welded headers when sealing
solder is applied to the air side and flows through the
leaking welded joints to the water side of the header.
Furthermore, the cost of the solder sealing used in
this invention is considerably less than the cost of
prior art air-side soldering by the use of perforated
foil or other specialty solder products because less
solder is used, the solder is purchased in inexpensive
form and no added shaping or perforation operation is
required, and the energy required to melt the solder for
dipping and in particular for wave soldering is less than
that to melt the solder foil or other specialty solder
product for air-side solder sealing.
Additionally, water side solder sealing according to
the present invention is found to be almost completely
effective in sealing sample cores, thereby eliminating
the need for rework of the air side solder which is
usually required by hand performed torch and wire solder
operations. Typically, five to ten joints in every motor
vehicle radiator core may require rework when utilizing
prior art methods. The present invention which utilizes
air side flux application and water side solder sealing
reduces leaks to a level which provide the possibility of
~'U(~~N4 r
-20-
eliminating individual leak testing of the radiators.
Furthermore, the appearance of the welded cores wherein
the solder is limited only to the leaks on each collar is
much more uniform and attractive than a core which has
been sealed on the air side and on which the solder has
run through to the water side on many of the joints.
When utilized in the method of the present invention,
wave soldering is significantly faster than the prior art
air side soldering techniques and reduces production
costs along with the labor and other expense of placing
perforated solder foil on the heat exchanger.
While the invention has been described with reference
to specific embodiments, it will be recognized by those
skilled in the art that variations are possible without
departing from the spirit and scope of the invention, and
that it is intended to caver all changes and
modifications of the invention disclosed herein for the
purposes of illustration which do not constitute
departure from the spirit and scope of the invention.
25
