BRAZING RING
BACKGROUND OF THE INVENTION
[0001] The subject matter disclosed herein relates to an autobrazing system and, more
particularly, to an autobrazing system having a brazing ring.
[0002] Round tube and plate fin heat exchangers (RTPF) used in air conditioners and
heat pumps generally include a series of long "U"-shaped tubes inserted into a densely
arranged pack of fins. The formed tubes, called hairpins, are then circuited (joined) to each
other at the opposite end by brazed-in-place return bends. At low production volumes, the
tubes are brazed manually. However, such manual brazing process is operator dependant,
susceptible to a higher defect rate and unacceptable in the high volume production
environments. Therefore, there is cost justification to automate the brazing process when the
production rates become sufficiently high.
[0003] Since conventional RTPF heat exchangers typically have copper tubes and
aluminum fins, the associated brazing process is forgiving due to a wide temperature window
between melting points of brazing material and copper tubes. Brazing automation for
aluminum tubes and aluminum fins, on the other hand, is new and requires relatively high
quality and high precision brazing to assure a leak/defect rate that is comparable to
copper/aluminum RTPFs.
BRIEF DESCRIPTION OF THE INVENTION
[0004] According to one aspect of the invention, a brazing ring is provided and
includes ring material including an aluminum-zinc-silicon alloy having a first melting point
and flux material contained within the ring material having a second melting point, which is
lower than the first melting point, the ring material being formed such that the flux material is
exposed to a heat source and such that, upon heating, flux material melts before the ring
material.
[0005] According to another aspect of the invention, an autobrazing system is
provided and includes first and second tubular members telescopically fittable to define first
and second annular spaces and a brazing ring fittable into the second annular space and
including ring material including an aluminum-zinc-silicon alloy having a first melting point
and flux material contained within the ring material and having a second melting point, which
is lower than the first melting point, the ring material being formed such that the flux material
is exposed to a heat source and such that, upon heating, flux material melts before the ring
material melts.
[0006] According to yet another aspect of the invention, an autobrazing system is
provided and includes a first aluminum tubular member having a tubular portion and a flared
portion at an end thereof, a second aluminum tubular member telescopically fittable into the
flared and tubular portions to define first and second annular spaces and a brazing ring
fittable into the second annular space and including ring material including an aluminumzinc-
silicon alloy having a first melting point and flux material contained within the ring
material and having a second melting point, which is lower than the first melting point, the
ring material being formed such that the flux material is exposed to a heat source and such
that, upon heating, flux material melts before the ring material.
[0007] These and other advantages and features will become more apparent from the
following description taken in conjunction with the drawings.
BRIEF DESCRIPTION OF THE DRAWING
[0008] The subject matter which is regarded as the invention is particularly pointed
out and distinctly claimed in the claims at the conclusion of the specification. The foregoing
and other features, and advantages of the invention are apparent from the following detailed
description taken in conjunction with the accompanying drawings in which:
[0009] FIG. 1 is a cross-section view of an autobrazing system with a brazing ring in
accordance with embodiments;
[0010] FIG. 2 is a cross-sectional view of the brazing ring in accordance with
alternative embodiments;
[0011] FIG. 3 is a cross-sectional view of the brazing ring in accordance with further
alternative embodiments; and
[0012] FIG. 4 is a cross-sectional view of the brazing ring in accordance with still
further alternative embodiments.
[0013] The detailed description explains embodiments of the invention, together with
advantages and features, by way of example with reference to the drawings.
DETAILED DESCRIPTION OF THE INVENTION
[0014] With reference to FIG. 1, an autobrazing system 10 is provided and includes a
first tubular member 20, a second tubular member 30 and a brazing ring 40. The first tubular
member 20 may be an end of a U-shaped tube disposed within a round tube plate fin (RTPF)
heat exchanger and has a tubular portion 2 1 and a flared portion 22. The tubular portion 2 1 is
substantially cylindrical with a substantially uniform diameter. The flared portion 22 flares
outwardly from an end of the tubular portion 2 1 and has an increasing diameter along a
length thereof. In some configurations, the flared portion 22 will be elevated above the
tubular portion 21. The second tubular member 30 may be an end portion of a return bend
tube by which adjacent U-shaped tubes of an RTPF heat exchanger fluidly communicate. The
second tubular member 30 is telescopically fittable into the flared portion 22 and the tubular
portion 2 1 of the first tubular member 20 to form a joint 45.
[0015] The first tubular member 20 further includes a first interior facing surface 211
at the tubular portion 2 1 and a second interior facing surface 212 at the flared portion 22.
Similarly, the second tubular member 30 further includes an exterior facing surface 301.
Thus, with this configuration described above, the telescopic fitting of the second tubular
member 30 in the first tubular member 20 defines first and second annular spaces 50 and 60,
respectively. The first annular space 50 is defined between the first interior facing surface
211 and the exterior facing surface 301 at the tubular portion 2 1 of the first tubular member
20. The second annular space 60 is defined between the second interior facing surface 212
and the exterior facing surface 301 at the flared portion 22 of the first tubular member 20. As
noted above, in some configurations, the second annular space 60 will be elevated above the
first annular space 50.
[0016] In some embodiments, the first and second tubular members 20 and 30 may be
formed of aluminum and/or aluminum alloys such that brazing processes should be carried
out within narrow temperature/time ranges to ensure high quality and high precision brazing.
[0017] The brazing ring 40 is fittable into the second annular space 60 such that it
may be suspended above the first annular space 50. The brazing ring 40 includes ring
material 4 1 and flux material 42, which is contained within the ring material 41. During
brazing processes, the flux material 42 cleans oxides off of the first and second interior facing
surfaces 211 and 212 and off of the exterior facing surface 301 to thereby facilitate
performance of high quality and high precision brazing processes.
[0018] The ring material 4 1 may include, for example, aluminum-zinc- silicon
(AlZiSi). In accordance with exemplary embodiments, the ring material 4 1 may include about
72% +7% (68-76%) aluminum, about 20% +7% (16-24%) zinc and about (4-12%) 8% +7%
silicon, the flux material 42 may have a minimum weight of about 0.08 grams and a
maximum weight of about 0.25 grams (a weight of between 0.3 and 0.6 grams) while the ring
material 4 1 may have a minimum weight of about 0.348 grams and a maximum weight of
about 0.6 grams (a weight of between 0.08 and 0.25 grams). A ratio of ring material 4 1 to
flux material 42 may be about 70-85% to 15-30% or, more particularly, about 71-81% to
about 19-29%. The use of the aluminum-zinc- silicon alloy assures a significant separation
between the melting point of the flux material 42 and the ring material 4 1 so that the flux
material 42 will tend to melt before the ring material 41. This is particularly suitable in
Aluminum-Aluminum brazing where the brazing temperature range is relatively narrow and
the respective melting points of the ring material 4 1 and the flux material 42 are provided at
opposite ends of the range.
[0019] The flux material 42 may be generally difficult to form into given particular
shapes, such as an annular ring. Moreover, once the flux material 42 is formed into those
shapes, the shapes tend to break down or otherwise fail during shipping, handling and/or
brazing process preparations. The ring material 4 1 serves to contain the flux material 42 in
the given particular shapes such that break downs and/or failures are avoided. For example,
where the flux material 42 is to be formed into an annular ring, the ring material 4 1 may be
formed into an annular groove surrounding the ring.
[0020] The ring material 4 1 has at least a first part 411 and a second part 412. The
second part 412 may be substantially larger than the first part 411. The ring material 4 1 is
formed in an annular shape such that the flux material 42 is contained within an annular space
within the ring material 4 1 and exposed outwardly. The flux material 42 is thus more exposed
to a heat source than the ring material 4 1 and the first part 411 is more exposed to the heat
source than the second part 412. Combined with the fact that the melting point of the flux
material 42 is lower than that of the ring material 4 1 it is to be understood that, upon heating,
the flux material 42 melts prior to any ring material 4 1 melting. Thus, molten flux material 42
flows into the first annular space 50 ahead of any molten ring material 41.
[0021] The molten flux material 42 flows into the first annular space 50 by capillarity.
Thus, a flow speed of the molten flux material 42 is maintained at a relatively slow pace to
encourage appropriate cleaning and brazing processes. In some embodiments, molten ring
material 4 1 is substantially prevented from flowing into the first annular space 50.
[0022] Where an amount of molten ring material 4 1 enters the first annular space 50
along with or ahead of the molten flux material 42, the amount may be limited to that of the
first part 411, which is more exposed to the heat source than the second part 412. Thus, the
amount of flowing molten ring material 4 1 may be small as compared to an amount of the
flux material 42 entering the first annular space 50 due to the first part 411 being substantially
smaller than the second part 412, which is shielded from the heat source and remains solid
during much of the brazing process. As such, the first and second interior facing surfaces 211
and 212 and the exterior facing surface 301 are properly and efficiently cleaned by the flux
material 42.
[0023] As shown in FIG. 1, the ring material 4 1 is formed with a J-shaped cross
section 70 whereby the flux material 42 is contained within the annular recess formed
between the short leg 7 1 and the long leg 72. In this case, the short leg 7 1 is proximate to the
second interior facing surface 212, forms the first part 411 and may be substantially thinner
than the long leg 72. Upon heating, therefore, the short leg 7 1 will either not melt until at
least all of the flux material 42 has melted or may tend to partially melt such that only a small
amount of molten ring material 4 1 will flow into the first annular space 50.
[0024] With reference to FIGS. 2-4, further alternative embodiments of the brazing
ring 40 are provided. In one alternative embodiment, as shown in FIG. 2, the ring material 4 1
may be formed with an I-shaped cross-section 80 whereby the flux material 42 is contained
within the annular pockets on either side of the vertical portion of the I-shape. In this case,
part 8 1 is proximate to the second interior facing surface 212, forms the first part 411 and
may be substantially thinner than part 82.
[0025] In other alternative embodiments, as shown in FIGS. 3 and 4, the ring material
4 1 may be formed with an inverted C-shaped cross-section 90 whereby the flux material 42 is
contained within the annular pockets in the center of the C-shape. In this case, end 9 1 is
proximate to the second interior facing surface 212, forms the first part 411 and may be
substantially thinner than end 92.
[0026] In accordance with further aspects of the invention, it is to be understood that
the materials and shapes of the first and second tubular members 20 and 30, the temperature
and timing of the brazing processes, the type of flux material 42 used and the geometry of the
ring material 4 1 are each interrelated. Therefore, decisions and/or design considerations as to
one or more of these affects decisions and/or design considerations of at least one of the
others. In particular, the materials and shapes of the first and second tubular members 20 and
30 may be determined initially. Based on that determination, the temperature and timing of
the brazing processes may be set. At this point, various types of flux material 42 may be
considered and, accordingly, various geometries of the ring material 4 1 may also be
considered as some flux material 42 types may require more or less structural containment as
provided by different ring material 4 1 geometries.
[0027] While the invention has been described in detail in connection with only a
limited number of embodiments, it should be readily understood that the invention is not
limited to such disclosed embodiments. Rather, the invention can be modified to incorporate
any number of variations, alterations, substitutions or equivalent arrangements not heretofore
described, but which are commensurate with the spirit and scope of the invention.
Additionally, while various embodiments of the invention have been described, it is to be
understood that aspects of the invention may include only some of the described
embodiments. Accordingly, the invention is not to be seen as limited by the foregoing
description, but is only limited by the scope of the appended claims.

CLAIMS:
1. A brazing ring, comprising:
ring material including an aluminum-zinc-silicon alloy having a first melting point;
and
flux material contained within the ring material having a second melting point, which
is lower than the first melting point,
the ring material being formed such that the flux material is exposed to a heat source
and such that, upon heating, flux material melts before the ring material.
2. The brazing ring according to claim 1, wherein the molten flux material flows
ahead of molten ring material.
3. The brazing ring according to claim 1, wherein the ring material comprises 68-
76% aluminum, 16-24% zinc and 4-12% silicon.
4. The brazing ring according to claim 1, wherein the ring material has a weight
of between 0.3 and 0.6 grams and the flux material has a weight of between 0.08 and 0.25
grams.
5. The brazing ring according to claim 1, wherein a ratio of ring material to flux
material is 70-85% to 15-30%.
6. The brazing ring according to claim 1, wherein the ring material is formed
with a J-shaped cross section.
7. The brazing ring according to claim 1, wherein the ring material is formed
with an I-shaped cross section.
8. The brazing ring according to claim 1, wherein the ring material is formed
with an inverted C-shaped cross section.
9. The brazing ring according to claim 1, wherein the ring material comprises
first and second parts, the first part being closer to a flow target than a second part, and the
first and second parts having first and second thicknesses, respectively, the second thickness
being thicker than the first thickness.
10. An autobrazing system, comprising:
first and second tubular members telescopically fittable to define first and second
annular spaces; and
a brazing ring fittable into the second annular space and including ring material
including an aluminum-zinc- silicon alloy having a first melting point and flux material
contained within the ring material and having a second melting point, which is lower than the
first melting point,
the ring material being formed such that the flux material is exposed to a heat source
and such that, upon heating, flux material melts before the ring material melts.
11. The autobrazing system according to claim 10, wherein the first and second
tubular members each comprise aluminum.
12. The autobrazing system according to claim 10, wherein the molten flux
material flows into the first annular space ahead of molten ring material.
13. The autobrazing system according to claim 10, wherein the ring material is
formed with a J-shaped cross section.
14. The autobrazing system according to claim 10, wherein the ring material is
formed with an I-shaped cross section.
15. The autobrazing system according to claim 10, wherein the ring material is
formed with an inverted C-shaped cross section.
16. An autobrazing system, comprising:
a first aluminum tubular member having a tubular portion and a flared portion at an
end thereof;
a second aluminum tubular member telescopically fittable into the flared and tubular
portions to define first and second annular spaces; and
a brazing ring fittable into the second annular space and including ring material
including an aluminum-zinc- silicon alloy having a first melting point and flux material
contained within the ring material and having a second melting point, which is lower than
the first melting point,
the ring material being formed such that the flux material is exposed to a heat source
and such that, upon heating, flux material melts before the ring material.
17. The autobrazing system according to claim 16, wherein the molten flux
material flows into the first annular space ahead of molten ring material.
18. The autobrazing system according to claim 16, wherein the ring material is
formed with a J-shaped cross section.
19. The autobrazing system according to claim 16, wherein the ring material is
formed with an I-shaped cross section.
20. The autobrazing system according to claim 16, wherein the ring material is
formed with an inverted C-shaped cross section.