Note: Descriptions are shown in the official language in which they were submitted.
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HIE~T EXÇHANGER ANI:)
METHOD OF ASSEMBI~ ?F
Back~round o~ the Invention
This invention relates to heat ~r.h~ngers and, more
part~cularly to motor vehicle heat exchangers or
radiators and to a method of joining the members thereo~
Users of heat exchangers, particularly those used in
automotive and truck engine~cooling radiators~ are
interested in achieving longer life in units which they
purchase. Truck manu~acturers are especially seeki n~ a
longer li~e radiator which can withstand the extra stress
and abuse in a truck environment for ~ignificantly longer
mileage.
The joints between the tubes and header~ in heat
exchangers in general, and automotlvQ type radiators in
particular, hav~ recaived increa~ed ~crutiny in the goal
to achlev~ longer ~ervice li~. Typically, the
tube-to-headQr joint had been a ~imple tin/lead ~oldered
joint between a thin walled bra~s tube and a thicker
header which ha~ a collared hola to receive the tube.
Because o~ ~p~n~ion and contraction of the tube during
the heating and cooling cycle pre~ent in operation, the
joint~ between the tubes and the heA~er~ are placed in
shear stress. Shock and vibra~ion in the ~otor vehicle
environment add to this stress. In addition, chemical
reactions between the coolant and any ~older which covers
the header ~urface on it~ water side can cause corrosion
produat~ which can flake off and clog the radiator tubes,
thereby leading to engine overheating.
,~
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Welding has been used to bond the tube~to-header
joint in order to strengthen this portion o~ automotive
radiators. However, current m~thods o~ welding do not
provide a completely leak-free welded joint in every
instance. To rectify this problem, it has been a
practice ~o apply a coating of solder on the air side of
all of the joint~ to seal any leak~ in th~ weld area
between the tube and header. This operation requires the
placement of ~r~n~i~e perforated solder foil or other
lo prefabrlcated ~orms of solder over the tube~ on the
radiator aore prior to assembly of the header to the
core. After welding the tu~e~ to the header collars, the
header is then dipped in flux and must be heated
extensively to cau6e the soldsr foil to melt and form the
sealant coating on the air ~ide of the header. During
this operation, solder flows through the usually numerous
tube-to-header joint leaks and con~iderabl~ ~older
appears on the water side of the header. This operation
is energy intensive, time consuming, and often causes the
header ~o warp due to the high temperatuxe~ in the
heating operation. Al~o, the core must normally ~till b~
tested to determine the int~grity of the tube-to-header
joint~. In 5pite of the air side solder coat~ny, there
may often A~pe~r several joints which remain un~ealed and
leak coolant ~luid. The~e ~oints must then be repaired,
usually by hand method6 such a~ u5ing a torch and wire
solder on the air ~ide of the joint.
Alternative methods of s~al~ng the tube~to-header
joints include applying flux to the liquid side of the
bonded joint and then applyiny a coating o~ solder, for
example, by dipping into a bath of molten solder or by
tha use of wave soldering techniques. These methods
result in lower header temperatures and thereby minimiza
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warping and the need for repair. However, the increased
amount of solder 1e~t on the water side sur~ace of the
header cre~tes a potentia1 for the creation o~ solder
corrosion products, a1so termed ~so1der b1Oom~.
Bearing in mind the problems and deficiencies of the
prior art~ it is there~ora an object of the present
invention to provide an improved tube-to-header joint for
use in heat exchangers and, in particulax, automotive
type radiatorsO
It is another object of the present invention to
provide a heat ~chA~ger in which the tu~e-to-header heat
exchanger joints are substantia11y leak-free.
It is a further object o~ 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 yet another ob~ect of the present invention to
provide a tube-~o-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 tubs-to-he~er heat exch~ser
joint which reduces the tota1 amount of so1der used,
uti1izes 1ess expensive so1der, and minimizes the e~ort
25 needed to apply the ~older during the prodllctioll o~ the
heat ~Y~-h~nger.
It is another object of the present invention to
provide a welded so1dQr sea1ed tube-to-header heat
exchanger j oint which can be readi1y manufactured by
30 mass-production techrliques and which results in an
improved produat.
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summa~ o~ the Invention
The above and other object~, which will be apparent
to those skilled in the art, are achieved in the present
5 invention which provides a m~ths:~d of a:Efixing a pluralit~
of tubes to a plurality o~ corr~spondirlg ops~nin~ in the
header wall o~ a heat exchanger in which the wall has an
inner, liquid-facing side and an outer, air-fac~ g side
by welding ends o~ thP tube~; to corresponding openings in
10 the header wall, such that the tubeE~ extend toward the
air-facing side of the wall, to form a plurality of
welded tube-to-header joints: applying flux to the
air-facing 5~ de of the tube-to header joints; and
thereafter applying a lead/tin or other solder to the
15 liquid-~acing ~ide of th~ ~ube-to-header ~oint and
flowing said ~older into any voids in the welded joints
to substantially ~eal the ~oint~ against leakage o~
liquid. Only those ~oints having potential liquid
leaking voids receive the ~older; ~ound, liquid-tight
welded joint3 are not ~older sealed.
PrePerably, the openings in the he~fler wall comprise
collars drawn or ~orm~d from ~he header wall.
Non-ciraular tube~, ~or sxample oval ~haped, can be
utilized and optionally, the tube end~ may he ~haped into
a sub~tantially circular cros~-section for insertion into
and through corre~po~ding circular collar opaning~ in the
header. Flu~ may be sprayed onto the air-~acing side o~
the tube-to-header joint and thereafter the molten solder
may be applied either by dipping the li~uid facing side
3 0 of the ; oint into a ba~h o~ mol~en solder or passing it
through a molten solder wave. Following ~;olidification
o~ the ~:;older, the liquid-~acing ~ide oî khe
tube-to-haader joint~; should be ~ubstantially ~rae o~
,
32~3~
soldsr to minimize corroslon product~ insidQ the heat
ch~nger during use.
Brief Desc~lption of the D~awin~
Fig. 1 i~ a side elevational view of the
cross-section of a pair o~ ~u~e-~o-he~r jolnts on a
heat eYçh~n~er header wall during the application of flux
in accordance with the method o~ the pre~ent invention.
Fig. 2 is a cros~-sectional view of th~ end of a heat
exchanger tube a~ seen along lines 2-2 in Fig. 1.
Fig. 3 is a side elevational cloee up view of a
cro~-section of a welded tube-to-header joint having
wQld voids.
Fig. 4 is a side elevational view showing a heat
exchanger during the solder application step in
accordance w~th the method of th0 pre~ent invention.
Fig. 5 is a cross-~ectional view of tube-to-header
joints produced in accordance with the method of the
present invent~o~.
Detailed De c~iption o~ the Invention
~efer~ncQ will be made herein to Fig~, 1 to 5 which
~5 detail var~ou~ portion~ of tha ~ethod and article of tAe
pre~ent invention. Unless otherwise Rp~sified, the
materials used to construct th~ heat eY~h~nger can be any
conventional mater~al for such use, such as aluminum or
the like. Like numerals refer to like features of the
invent~on throughout the drawing~.
In Fig. 1 there is shown a portion of the heat
exchanger made ln accordance with the present invention.
Heat exchanger tube~ lO are provided to carry the working
' ~320~c~
fluid o~ the heat ~c.h~n~er to any ~ins (not shown) and
between opposed header~ a wall of which i5 shown as 16.
As ~een in Fig. 2 in an axial cross-section transverse to
its longit~ n~l axis, the ma~n body portion o~ ~ube 16
has a generally oval or elliptical shape 12, the end
portions 14 of which have been shap~d into a
substantially circular cross-~ection~ Optionally, the
tube body portions may have other cros~ sectional shapes
and the tube end may be o~ any shape for which a
corresponding opening in the header wall ~ay be made.
The header wall or plate 16 ~hown iB oriented with
the air-facing side l~a ~acing upward and the
liquid-facing side 16b facing downward~ as seen in Fig.
1. Header wall 16 includes a ~eries of openings in the
form of in~egral drawn collars or ~lange~ 18
substantially con~orming to the shape of tube end
portions 14. As ~hown in Fig. 1, circular tube ~nd
portions 14 are received within and extending through
circular collar openings 18 formed in wall 16. The tube
body portions extend away and outward ~rom th~ joint on
the air ~ide of the headar wall. Aftsr the tube ends are
in~erted into the collar open;ncJs, they may be optionally
sized to provide a tight comprQs~ion typa fit betwe~n the
tube end. and the collar opening, ~or example, by the
method taught in U.SO Patents 4,744,505 and 4,858,686,
the disclosuras of which are herein incorporated by
reference, wherein the tub~ and~ are sub~tantially
coplanar with the end~ of collar 18 and the outermo~t
tube end portion is ~r~n~P~ to ~orm a tight fit with the
lip o~ the collar.
Following the tube in~Qrtion step, the tube ends are
bonded to the header wall collar openings 18 by welding.
This proce~s may be performed by any known method, ~or
'" 2~2~3~
example, ~y thos~ disclo6ed in the aforement.~on~d uos~
Patent~ or those methods di~c1O~2d in U.S. Patents
4,377,024 a~d 4,529,034, the disclosurQ~ of which are
also incorporated by reference. The ~ini~h~d welded
tube-to~header joints are shown as weld bead~ 20' and
20~.
In the course o~ produ~-ing a welded or otherwise
bonded tube~to-header ~oint, voids may be present which
present the possibility of liquid leakage from the liquid
side of the header through the ~oint to the air side of
the header. Typical void~ 22 are shown in welded joint
20'~' in the closeup of Fig. 3 wherein the voîd 22
comprises a narrow opening between the liquid and air
sides o~ header wall 16. Void 22 iE~ shown a~ a
15 chann~l-like opening here only ~or purposes of
convenience - such voi~s may be o~ numerou~ othar 6hapes
such as gas pockets ~ormed in a wald bead, cracks formed
upon heating or cooling of the w~ld bead, or area~ in
which the welding or bonding ha~ bQen inaompletely made~
20 The term nvoid~ i8 intended to aover these and other
potential liquid-le~k~ng op~nings in the joint. In any
event, such voids 22 may or may not be present in every
joint, as ~hown in Fig. 1 wh~rein void 22 is pre~ent in a
fir6t welded joint 20', but absent from a second welded
25 joint 20N. It i5 common that at least a portion of, but
not all, of thQ welded ~oin~; in ~ motor ~hicle type
radiator may contain such void~. The pre~ent invention
i~ directed to a method which result~ in a completed heat
e~çh~nger in which only those welded joints having voids
are sealed hy ~older, and those welded joints in which
there are no leak cau~ing void~ ar~ nDt sealed by any
solder.
~32~
-8-
Re~erring back to Fig. 1, following the welding o~
the tube ends to the he~er wall, the heat exchanger is
preferably positioned on its side so that the
tube--to-header joints face downward, i.e., the haader
wall 16 is usually horizontal and the tube bodie~ extend
upward and vsrtically from the tube~to-header joints. A
solder flux type material iB shown being sprayed by
nozzles 24 illtO the upward air side 26 of each
tube-to-header joint. These fluxes may be any typ
conventionally used in soldering which are capable of
being applied in the manner contemplated by this
invention . Each ; oint in a given heat exchanger is
sprayed with flux in thi~; manner so that in those joints
having voids which pre~ent the potential for liquid
15 leakage, the flux may thoroughly coat the area and flow
ds~wnwar~ into the void it~elf either by gravity or
capillary act~ on, or both. The usually limited ~ize o~
the voids which may be present in any of the
tube-to-he~der ; oints prevents PYc~ive amounts o~ the
20 ~lux from running through or around to the water-faclng
side of the he~rler plate.,
Subsequently, as illustrated in Fig. 4, the welded
and fluxed tube-to he~r ~oints o~ the heat ~Ych~nger
are ~ubjected to a ~oldering operation by c:ontacting the
25 liquid ~acing ide o~ the tube-to-header ~oint with
solder, ~or example, by dipping into molten solder. The
pre~erred method utilize~ a solder wave device 28 which
employs a solder pump 30 to ~orm an upward directed
molten solder wave 32. The header tu~e assembly 34 is
shown on its side to present the downward facing ~oints
20 to the molten solder. Heat exchanger ~ins 40 are
shown partially over heat exchanger tube array 36. Such
...... .... . .. . . . . .
3 ~
fin~, when they are employed, may be i~stalled over the
entire fln array ei~her before or a~ter the 601dering
method of the present invention.
~ uring the soldering process, header t~be assembly 34
5 iB moved to the right, as shown by the arrow in Fig. 4,
to present thP downward ~acing joints ~or contact with
the ~olten solder wave 32. ~he ends of the
tube to-header joints 20 are immer~ed in the molten
solder only to a degree sufficient to draw the solder up,
by capillary action, through any voids pre~ent in those
joints. A solder fillet may be formed o~ the air side of
any ~uch join~. As practiced by the pra~ent invention,
the ~oints are not exposed to any more heat than i~
necessary to apply the molten ~older in thi~ fashion.
Furthermore, because of the application ~ethod, the
solder employed may be of the relatively inexpensive type
u~ed in ~uch molten solder application device~, and need
not be the more expensive Poil or wire type soldex
utilized in the prior art. Joints which have no voids or
2 0 cracks do not draw up any solder an~, consequently, no
solder fillets are formed on eikher the air or water side
of any sound joints. Following solidificatiorl, the only
solder which remains on the water side of the he~r is
that which ac~ual~y seals ths vo:Lds in tho6e
25 tube-to~header ~ oints that have th~m. ~here i~
essentially no surfaca coYerage by ~older on the water
side o~ the header wall because ~luxing is limited to lthe
voids only, and therefora the water side of the header
wall (aside from the voids themselve~) remains
substantially solder free to prevent e~cessive solder
bloom corrosion.
., .. . ,, : .
3 ~
--10--
Typical completed tube-to-header joint$ made in
accordance with the pr~ ent invention are illustrated in
Fig. 5 which ~hows a pair of tubes 10 and lOa joined to
head~r wall 160 Tube 10 on the left is secured to the
h~ r wall by welded joint 20' which initially included
a pair of ~oids 22 through the joint fro~ the liquid ~o
the aix side. As a result of the flux~g and soldering
operation o~ the present invention, void~ 22 have been
sealed by solder which has been drawn up through the
~0 voids by capillary action to eal not only vold 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-facing side of thi6 ~oint, essentlally no solder
~ n~ on the liquid side o~ joint 20'. The othar tube
lOa is shown as having been initially sealed to header
wall 16 by a sound wslded ~oin~ 20~ which cont~neA no
void6 which would provide potential points of leakage.
Although the welded joint 20~ also had flux applied on
its air side and contacted with molten solder on it6
liquid side during ~he soldering opera~ion, the soundnes~
of the joint prevented any ~lux ~rom pa~sing through to
the liquid sida. Thus, joint 20 is also ~ubstantially
free of solder on both it8 air side and liguid side.
Following the solder application step o~ the present
invQntion, the manu~acture o~ the heat ~Ych~nger may be
continued and comple~ed by bon~n~ the header tank~ onto
th~ respecti~e header walls and aecuring the ~ins over
the tubeB ( if thi~ latter operation had not been done
previously~ by any conventional methods such as ~hosa
dQscrib~d in the a~oremen~ioned U.S. Patents.
~ he method of applying the flux and soldQr sealing of
welding joints accordin~ to the present invention results
in a welded radiator product which ha~ less ~older on the
~2~
water aide of the header than prior art ~ethods.
Furthermore, the mas~-produced heat exchangar which
results from this m~thod is unigue in that soldar appears
on the water side of the header only where void sealing
5 i8 reguired, and ~older appear~ on the air side of the
header as a fillet around only thos~ tube-to-header
joints which require th~ 6ealing of a void. ~hus the
pr~sent invention result& in welded tube-to-header ~oints
with greatly increa~ed strength over soldered joints with
the advantage of minimizing the amount o f ~older in
contact with the coolant and effectiYely eliminating the
undesirable effects of solder bloom corrosion. The
actual amount of solder coating is limited to tha
location o~ actual leak~ and i~3 only a fraction of the
15 amount of solder employed in a solder dipped header.
This amount o~ solder is considerably less than the
amount created on prior art welded he~er~; when ~~ealing
solder i8 appliQd to the air side and ~lows through the
le~k i ng welded joint~ to the water slde of ths h~er .
Furthermore, the C08t of the solder sealing u~ed in
this invention i~ considerably 1~SB than the cost of
prior art air soldering by the use o~ perforated fo~l or
other specialty solder productB becauBe le68 solder i~
used, the solder i purchased in ;n~Y~n~ive form and no
added shaping or perforation operation is re~uired, and
thQ energy required to melt the solder for dipping and in
particular ~or wave soldering ls less than that to melt
the solder ~oil or other specialty solder product for
air-~ide solder sealing.
Additionally, water side solder sealing according to
the pres~nt invention is found to be almost completely
effective in seal~ng ~ample cores, thereby eliminating
the need ~or rework o~ the air side so~der which is
2~3~
usually required by hand performed torch and wirs solder
operations. Typically, five to ten joints in every motor
vehicle radiator core may require rework when utilizing
prior art methods. The pre~ent invention which utilizes
air side ~lux application and water side solder ~ealin~
reduces leaks to a level which provide the po~ibility of
eliminating individual leak te~ting o~ the radiators.
Furthermore, the appearance of the welded cores wherein
the solder is limited only to the lea~s on each collar is
much more unlform and attractive than a core which has
been sealed on the air ~ide and on whlch the ~older ha~
run through to the water side on many o~ the joints~
When utilized in the method o~ the present invention,
wave ~oldering is significantly faster than the prior art
air side oldering technique~ and reduces production
costs along with the labor and cther expense o~ placing
per~orated solder foil on the heat ~Y~h~nger.
While the invention ha~ be2n described wlth reference
to specific embodimen~s, it will be reco~nized by those
~killed in the ar~ that variations are po~sible without
departing from the ~pirit and scope of the invention, and
that it is lntended ko cover all changes and
modifications o~ the inven ion disclosed herein ~or the
purpose~ o~ illustration which do not constitute
departure from the ~pirit and scope o~ the invention,
Having thu~ described the invention, what l claimed
is:
