Note: Descriptions are shown in the official language in which they were submitted.
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079031-LC -1-
METHOD FOR REINFORCING H~AT EXCHANGEP~
TUBE TO HEADER JOINTS
Description
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Heat exchangers in the past have utilized re-
inforcement plates ~here the tube to header joints are
unsatisfactory or the stresses exerted in the heat
exchanger structure are concentrated at the outer tuhe
edge solder joints. Bolted radiator core assemblies
have located reinforcement plates in the four corners
of the core; these reinforcement being relatively short
in length. Other assem~lies require a long reinforcement
plate or have used a reinforcement plate of substantially
the same dïmensions as the header plate so that the
edges of both plates must ~e secured and sealed to the
headers by bolting, etc.
The header and reinforcement plate tube holes are
punched, lanced and/or form punched separately. I'he
two parts are then placed together, aligned and joined
by suitable means, such as spot welding, riveting
and/or soldering. The tubes are then installed in the
header assembly and soldered. These methods require
complex tooling to duplicate results and have problems
of mismatch where long reinforcements are made. These
present reïnforcements are not consistent in providing
2S void free joints and require separate dies for the
header and reinforcement plate. The present invention
relates to an improved way of distrihuting the stresses
that exist in the tube to header solder joints.
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The present invention relates to a novel method of
reinforcement of the tube to header join-ts in a heat
exchanger assembly. High stresses develop in these joints
due to vibration and also due to thermal stress development
occurring from the differential expansion of the core and
the heat exchanger structure. Essentially, this method
requires a preliminary joining operation of a reinforcement
plate to the tube header plate followed by a hole punching
operation on the assembled plates to provide the tube holes,
; 10 the insertion of the tubes thereinto and soldering of the
tubes to the header and reinforcement plate. This method
allows for complete flexibility in selecting various material
; thicknesses for both the header and reinforcement plate to
;~ suit the heat exchanger application and, at the same time,
achieving a perfect mate between both plates. This
flexibility is essential when matching the durability required
by the heat exchanger where numerous thermal fluctuations are
present requiring a thin header and a thick reinforcement
plate. When the heat exchanger is subjected to high shock
loadinys, then a thick header and thick reinforcement plate
are necessary. These changes can be accommodated with little
or no tooling change.
More specifically the present invention relates to a
method of reinforcing heat exchanger tube to header joints,
the method including the steps of cutting a tube header plate
to size and providing a reinforcing plate of smaller dimensions
than the tube header plate and then joining the reinforcing
plate to the tube header plate by spot welding, soldering,
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welding or brazing. Tube openings and -then formed
simultaneously through the joined plates, and a tube is
inserted into each aligned pair of openings in the plates
to form a joint solder then being applied to the joint area.
The present invention also comprehends the provision
of a reinforcement plate joined to the tube and header to
provide reduced stresses in the solder joint at the outside
tube outer edge. Essentiall~v the invention (1) provides a
higher solder joint bond area parallel to the longitudinal
axis of the tube around the tube periphery; (2) stiffens
the area onto which the reinforcement is placed, thus
distributing the
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079031-LC -3-
: stresses more evenly around the tube solder joint and
into adjacent tube joints; and ~3~ moves the stress
concentrations at the weak solder joint at the outer
tube edges into the strong header plate material at the
outside edges of the reinforcement.
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The present invention further comprehends the pro-
vision of a reinforcemer.t plate joined to a tu~e header
, which eliminates mismatch of openings where long re-
: inforcements are required, eliminates the use of complex
toolïng to duplicate results, and provides for an ex-
cellent solder draw and bond between all three components;
namely the tube, tube header and reinforcement plate.
Further obj'ects are to provide a construction of
maximum simplicity r efficiency, economy and ease of
assembly, and such further objects, advantages and
capabilities as ~ill later more fully appear and are
inherently possessed thereby.
One way of carrying out the invention is described
in detail below with reference to drawings which illustrate
only one specific embodiment, in which:
Figure 1 is an exploded perspective view showing
the alignment of a header and reinforcement plate to be
joined in the present method.
Figure 2 is a perspective view of the h,eader and
reinforcement plate joined together.
Figure 3 is a perspective vle~ of th,e. joined
plates with the tube openings punched therein.
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Figure 4 is an enlarged cross sectional vie~ taken
on the line 4-4 of Figure 3.
Figure 5 i5 a cross sectional view similar to
Figure 4, but with the tu~es inserted into the openings.
Figure 6 is an enlarged cross sectional view
similar to Figure 5, but showing a solder joint for a
tube.
Figure 7 is a perspective view of a core for a
heat exchanger having a plurality of tuhes extending
between and joined to reinforced headers.
Figure 8 is a top plan view of the reinforced
header and tu~es of Figure 7.
Figure 9 is a cross sectional v;ew of a presently
utilized reinforcement joint having a lanced header and
punched reinforcement.
Figure 10 is a cross sectional view of another
presently used reinforcement joint with a formed-
punched header and reinforcement.
Referring more particularly to the disclosure in
the dra~ings wherein is sho~n an illustrative embodiment
of the present invention, Figure 1 discloses the first
step in the formation of a reinforced tube header of
the present invention wherein a tuhe header lQ cut to
required size and adapted to be utilized in a tube and
fin core for a heat exchanger (not shown) has a re~
inforce~ent plate 11 cut to required size and aligned
079031-LC -~-
thereon as shown by arrows A. Once positioned, the
tube header plate and reinforcing plate are spot welded,
welded, soldered, brazed or otherwise joined together
at a plurality of locations 12 approximately 2" to 3"
apart adjacent the periphery of the plate 11; the
header plate 10 having a border 13 exposed by the plate
11 adapted to be clamped or otherwise secured to an
inlet or outlet tank of a heat exchanger.
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The asembled tu~e header-reinforcement plate is
then placed in a form-punch or punch single hit die to
produce the tube hole pattern (see F~gure 3) having the
rows of openings 14 and 15 through the reinforcing
plate 11 and tube header 10, respectively. This die
may punch all of the openings simultaneously or pro-
gressively as more clearly shown in Figure 4, As seen
in Figure 5, the tubes 16 of the core are inserted into
the openings 14, 15 and solder is applied. The solder
draw is excellent to provide void free joints 17 at the
tube and the reinforcement plate-tube header outer
edges 18, 19, respectively. As seen in Figure 6, not
only is the solder joint 17 void free but a small
quantity of solder 21 is drawn between the reinforce-
ment plate 11 and header 10. Also, solder 17 is drawn
between reinforcement plate edges, header edges, and
tube 13, 19 and 16, respectively, and a bead 22 of
solder forms at the depressed edge 18 of the plate 11.
The distance between the outer ed~e 23 of the
reinforcement plate 11 and the tube tip 24 has a
minimum acceptable dimension. This is determined so
that there is no distortion of tke reinforcement plate
11 producing a gap between the header 10 and reinforce-
~ ment 11. Figure 7 discloses an assem~led tu'oe core 25
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079031-LC -6-
having reinforced headers ~6 at each end to be secured
to the inlet and outlet tanks of a heat exchanger.
Figure 8 discloses the finished header 26 with the
tubes soldered therein. Voids 27 are present betwean
the header and reinforcement plates and between the
tubes 16 but the structural performance of the header
is not effected.
The above descri~ed method overcomes many problems
associated with producing effective reinforced ~oints.
It eliminates the use of complex tooling for duplication
of results and provides for complete flexibility in
changing material thicknesses without die changes. As
shown in Figures 9 and 10, presently used types of
reinforcement are not consistent in providing void-free
joints. As seen in Figure 9, the header 31 has lanced
openings 32 and the reinforcement plate 33 has punched
openings 34. After the hole forming operations, the
plates are aligned and joined by spot welding, riveting
and/or soldering, the tubes 35 inserted in the openings
and soldered. As seen, the solder 36 does not provide
a void-free joint, as evidence by the voids 37. As
above noted, two separate dies are required to produce
the tube header and reinforcement plate. Also, stock
thickness on the header cannot be varied without a die
change. If a pro~ressive die is used to punch the
header and/or reinforcement tube holes, serious mismatch
ma~ occur in producing a long reinforcement. To eliminate
the mismatch, piercing small sections together will
solve the problem, but it is cumbersome.
In Figure lQ, both the header and reinforcement
plate openings are formed ~y the same die. As shown,
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the header 41 has form-punched openings 42 and the
reinforcement plate 43 has form-punched holes 44. When
` joined together, the header 41 and reinforcement plate
43 do not mate, resulting in gaps 45 therebetween.
When the tube 46 i5 inserted and solder 47 applied,
voids 48 may be possible.
