Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to heat excllanclers, and in
particular to heat exchange tubes used therein.
In the past, heat exchan~ers have heen made
consisting of a plurality o discreet heat exchancle tuhes
mounted in and communicating with common headers. Such
heat exchangers typically have a plura]ity of stacked,
transverse, heat transfer fins connected to the tubes, or
serpentine heat transfer Eins located hetween and parallel
to the tubes. These heat exchangers are often made of
brass or tinned steel and the mating surfaces are soldered
to produce rigid, leak-proof joints.
A difficulty with the prior art methods of
construction is that thermal expansion and contraction
during assembly makes it difficult to maintain dimensional
tolerances and it often causes leak problems due to poorly
formed solder joints. In an attempt to overcome such
difficulties, efEorts have heen made to deEorln mating
components to mechanically lock or bond them togetller.
However, it is not always possible practically to
mechanically lock all of the joints necessary to overcome
these difficulties.
Another problem with the prior art construction
methods is that heat exchangers are often made from one or
more subassemblies which are completed hefore Einal
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assembly. If the subassemblies are soldered together and
soldering is used in the final assembly, the latter
soldering operation can disrupt or dislocate the components
of the subassemblies, again playing havoc with the
dimensional tolerances of the heat exchan(~ers.
In the present invention, locatin~ bulges are
formed in the heat exchange tubes to locate and retain the
various components in position durin~ assembly.
Accordin~ to one aspect of the invention, there
is provided a method of manufacturing a heat exchange tube
for use in a heat exchanger. The method comprises the
steps of providing a heat exchange tube having an open end
portion and supporting the tube adjacent to the open end
portion to prevent lateral expansion of the tube where
supported. The distal end of the open end portion of the
tube is gripped, and high pressure fluid is injected into
the tube to produce a locating bulge in the open end
portion spaced ~rom the gripped dista] end.
According to another aspect o the invention,
there is provided a method of producing a tube to header
joint in a heat exchanger comprising the steps of providing
at least one heat exchange tube having an open end portion,
providing a header having means defining an opening adapted
to accommodate the tube open end portion, and supporting
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the tube adjacent to the open end portion to prevent
lateral expansion of the tube where supported. The distal
end of the open end portion of the tube i9 gripped and high
pressure fluid is injected into the tube to produce a
locating bulge in the open end portion spaced from the
gripped distal end. The tube is inserted into the header
opening so that the means defining the header opening
engages the tube locating bulge, and the joint between the
header and the tube is sealed.
According to yet another aspect of the invention,
a method of manufacturing a heat exchanger is provided
comprising the steps of providing a plurality of parallel
heat exchange tubes each having at least one open end
portion, providing a header having means defining a
plurality of openings adapted to accommodate the tube open
end portions, and supporting the tubes adjacent to the open
end portions to prevent lateral expansion of the tubes
where supported. The distal ends of the open end portions
of the plurality of tubes are gripped and high pressure
fluid is injected into the tubes to produce locating bulges
in the open end portions spaced from the gripped distal
; ends. The tubes are mounted in the header, so that the
means defining the header openings engages the tube
.
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locating bulges, and the joints between the header and the
tubes are sealed.
According to yet another aspect Oe the invention
there is provided a heat exchanger comprising a plurality
of parallel heat exchange tubes, each tube having a open
end portion. A header is mounted on an communicates with
the open end portions, and each tube has a lateral locating
bulge adjacent to the header and spacec3 ~rc~m the end of the
tube for locating and retaining the header in position.
According to yet another aspect of the invention,
there is provided apparatus ~or manufacturing heat exchange
tubes for a heat exchanger having a plurality of heat
exchange tubes each having an open end communicating with a
common header. The apparatus comprises means ~or
supporting and preventing lateral expansion of the heat
exchange tubes at a location spaced from the ends of the
tubes. A fixture is provided for engagin~ the open ends of
the tubes prior to assembly with the header, the fixture
having means for injecting high pressure fluid into the
tubes to produce locating bulges adjacent to and spaced
from the ends of the tubes, so that upon assembly of the
heat exchanger the locating bulges engage and locate the
header in position.
` - 6 - 1313184
According to yet another aspect of the invention
there is provided apparatus for manuEacturing a heat
exchanger having an assembly o a plurality oE heat
exchange tubes mounted in a common header, tlle tuhes having
locating bulges formed therein engaging the header. The
apparatus comprises a jig for holdin~ the tube and header
assembly and means for biasing the header into engagement
with the tube locating bulges, so that the tuhe and header
assembly can thermally expand and contract during final
assembly.
Perferred embodiments of the invention will now
be described, by way of example, with reEerence to the
accompanying drawings, in which:
Figure 1 is a perspective view, partly exploded
and partly broken away, of a preferred embodiment Eor a
heat exchanger made according to the present inventi.on;
Figure 2 is a vertical sectional view taken along
lines 2-2 of Figure 1 showing part of the assemhled heat
exchanger of Figure l;
Figure 3 is a vertical sectional view oE a
portion of the apparatus used to form bulges in the ends of
the heat exchange tubes shown in Fi~ure 2;
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Figure 4 is an elevational dia(lralncltic view oE
the apparatus used in the final assembly o~ the heat
exchanger of Figure l;
Figure 5 is a p~erspec~ive view sirnilar to Fiqure
1 but showing another embodirnent Oe a heat exchan(~er made
according to the present invention, but having serpentine
heat exchange fins; and
Figure 6 is an elevational view of a portion oE
the heat exchan~er oE Fi~ure 5 indicate(l by arrow fi in
Figure 5.
Referring first to Fi~ure l, a heat exchanger
made according to the present invention is generally
indicated by reference numeral 10. Heat exchan~er 10
includes a plurality of heat exchan~e tuhes 12 and a pair
of opposed headers 14 mounted on and enga~ing the ends of
tubes 12. A plurality of thin, parallel heat exchange
fins 16 is mounted on tubes l2, only solne oE whicll are
shown in Figure l, the chain dotted lines indicatin~ a
series of additional fins to fill the nain body of heat
exchanger 10. Heat exchanger 10 also has a central
stiffener plate 18 although this may be o-nitted iE
desired.
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As seen best in Fiqures 1 and 2, heaclers 14 have
inner plate portions 20 definin~ a plurality of or)enin(~s 22
formed therein. Openings 22 are su~roun(1ed hy inwardly
projecting flanges or ferrules 24 to accommodate upper end
portions 26 of tubes 12. Openings 22 are elon~ate in shape
to accommodate tubes 12 which are flat or oblong in
cross-section, but tubes 12 could be circular in
cross-section in which case openings 22 wolllcl be circular
as well.
Headers 14 also have outer housing portions 28
joined to plate portions 20. Housing portions 28 have
central nipples 30 forming an inlet in one header 14 and an
outlet in the other header 14. Headers 14 are typically
formed of brass or bronze and they may be cast or Eormed of
separate pieces mechanically joined in a Eluid-tight
manner, or made in any other convenient manner. The exact
configuration of headers 14 is not important to the present
invention, it is only necessary that the headers have a
plurality of openings 22 corresponding to or in
registration with the heat exchange tubes 12, so that fluid
may flow from one header through the tubes to the opposite
header.
Heat exchans~e tubes 12 are typically formed of
brass and are pre-soldered or solder coated on the outside.
9 1313184
The tubes may be seamless or seamed. Heat exchange fins 16
may also be formed of brass or aluminum, tin-plated brass
being preferable, so that the fins 16 may be soldered to
tubes 12, as described further below. It will be
appreciated, however, that other materials could be used
for the headers, the fins and the tubes, and further that
the various components could be connected or assembled by
brazing, by soldering or even by adhesive or elastomer
bonding, whichever is most appropriate for the materials
used. All of these methods of connection or assembly, for
the purposes of this disclosure, come within the term
"sealing" as it refers to the tube to header joints.
Referring in particular to Figure 2, it will be
seen that fins 16 also have flanges or ferrules 32 which
space fins 16 apart at equal intervals. The stiffener
plate 18 also has ferrules 34 through which tubes 12 pass.
The open end portions 26 of heat exchange tubes 12 include
bulges 36 for positively locating headers 14 relative to
fins 16 as will be described further below.
Referring next to Figure 3, the apparatus for
forming bulges 36 in tubes 12 is shown. Bulges 36 are
shown in chain dotted lines in Figure 3, tubes 12 being
shown in full lines prior to the formation of the bulges.
The heat exchange tube manufacturing apparatus inlcudes a
pair of fixtures 38 which engage the open ends of tubes 12
by means of hollow dies 40. Each die 40 has an inner wall
42 which is shaped to accommodate the peripheral end of a
1 31 3 1 8~
tube 12 with a relatively loose or sliding fit. Each die
40 also includes an inner wed~e memher 44, which toclether
with inner wall 42 forms a V-shaped annular ~roove into
which the peripheral end of tube 12 is wedged to form a
seal to prevent fluid flow from inside tube 12 out around
the peripheral edge of the tube. Each die 40 also includes
an outer wall 46 which forms an expansion chamber 48 to
allow the formation of bulges 36. Inner wedge memhers 44
also include flow passages 50 for injecting high pressure
fluid into tubes 12 as described and explained below.
The assembly of tubes 12 and fins 16 forms a heat
exchanger core 51 to which ,headers 14 are assembled to form
the complete heat exchanger 10. However the tubes 12 may
be formed separately for use in another type of heat
lS exchanger as will be described further below with reference
to Figures 5 and 6.
To manufacture heat exchange tuhe 12, a plurality
of fins 16 are slipped onto tubes 12, so that tlle ferrules
32 of the thusly stacked fins collectively form means for
rigidly supporting the tubes intermediate the tube open end
portions 26. The fins 16 and the stiffener plate 18, where
it is employed, and in particular tlle ferrules 32, 34
thereof form means for preventing lateral expansion of
tubes 12 during the manufacture of the tubes. I~owever,
- 11 13t31~4
where it is desired to make tubes 12 without fins 16 or a
stiffener plate 18, a suitable fixture or other rigid
retaining device could be used to preven-t lateral expansion
of tubes 12 as will be apparent to those skille~ in the
art.
Once fins 16 and stiffener plate 18 are slid onto
tubes 12, or some other rigid member supporting device is
put into place to prevent lateral expansion of tuhes 12,
dies 38 are placed over the open end portions 26 of tubes
12 and forced together to sealingly engage the peripheral
ends of the tubes 12. High pressure fluid as indicated by
arrows P in Figure 3 is then injected into tubes 12 to
cause bulges 36 to be formed in the open end portions 26.
The high pressure fluid is typically compressed gas at a
15 pressure of about 1,000 psi (6900 kPa.). A liquid or other
hydraulic fluid could be used for the high pressure fluid,
but this would be messy and may necessitate a subsequent
cleaning operation. With the bulges 36 formed, fins 16 are
held in position forming core Sl, which is then ready for
the final steps of the manufacture of heat exchanger 10.
Referring again to Figure 1 and also to Figure 4,
headers 14 are then slid over the open end portions 26 of
tubes 12 until ferrules 24 engage bulges 36. It will be
appreciated that all of the components of heat exchanger 10
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are thus positively located by bulges 36. It will he noted
also that ferrules 24 have rounded shoulders 52 and
slightly inwardly inclined wall portions 54 (see Fi-Jure 2).
This provides more surface area contact between the tuhes
and the headers and this improves the seal and the strength
of the tube to hea-3er joints.
Where the components oE heat exchanger ln are
formed of brass, pre~erably pre-soldered or tinned ~nd then
coated with flux and/or solder paste prior to assembly, the
assembly may then be put into a bake oven to complete the
soldering operation, and in connection with this a jig 56
is used, as diagramatically illustratec3 in Figure 4.
Jig 56 includes a frame 58 having central
retaining elements 66 for holding the assembled heat
exchanger core 51 and headers 14 in place. Transverse
bearing members 62 support sliding shats 64, wllich slide
toward and away from the pre-assembled heat exchanqer lO.
Clamping members 66 are connecte-3 to the inner ends of
shafts 64. Clamping members 66 press inwardly against
headers 14 to holc3 the headers unto core 5l durin~ the
soldering operation. L-shaped members 68 are pivotally
mounted in brackets 70, and weights 72 mountec3 on the outer
ends of L-shaped members 6~, cause the L-shaped members 6n
to bear against sliding shafts 64 and thus ur~e or bias
1313184
clamping members 66 against headers 14.
Actually, jig 56 is shown in a vertical.
orientation in Figure 4 for illustration purposes only.
Jig 56 would normally be horizontal and hracl<et 70 would he
mounted above bearing members 62, so tllat weights 72 move
downwardly to bias sliding shafts 64 toward heat excllanger
10. It will be appreciated that tlle conEi-luration of
weights 72 is not important, it is only necessary that
clamping members 66 be biased toward headers 14 to hold the
headers onto core 51 during the soldering operation. In
fact, the L-shaped members and weights could be replaced by
springs or some other type of biasing means if desired. ~y
biasing headers 14 into engagement with core 5l, the header
ferrules 24 stay in contact with bulges 3fi, even thou~h
core 51 expands and contracts as it is heated and cooled
during the soldering operation.
Referring next to Figures 5 and 6, another
embodiment of heat exchanger 10 is shown havi.n~ serpenti.ne
fins 74 located between and parallel to tubes l2.
Serpentine fins 74 fit snuggly between respective heat
exchange tubes 12 and are soldered in place simultaneously
with the soldering of heat exchange tuhe 12 to headers l4.
Otherwise, the heat excllanger of Figures 5 and 6 5 is
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identical to that of Figure 1. ~o make the bulges 36 in
heat exchange tubes 12, however, the rigid members
surrounding the tubes, such as the stacked fins 16 shown in
Figure 3 would be rernoveable af-ter the bulge forming
operation. For this purpose, the stack of fins would be in
two halves or split in a plane intermediate and parallel to
the longer sides of the stack of fins. Alternatively, and
perhaps preferrably, a solid, two-part mold would be used
in place of the stack of fins.
From the above, it will be appreciated that the
manufacturer of the heat exchanger of the present invention
results in a product with very close dimensional
tolerances, good tube to header seal and joint strength
with reliable soldered joints. Even where the heat
exchanger core is assembled and soldered prior to fitting
the headers onto the core, the soldering of the headers to
the core does not result in displacement or relocation of
the fins or dimensional variations in the spacing between
the headers.
