U.S. patent application number 11/916459 was filed with the patent office on 2008-09-25 for fully-metal heat exchanger and method for its production.
Invention is credited to Helmut Roll.
Application Number | 20080230213 11/916459 |
Document ID | / |
Family ID | 36123144 |
Filed Date | 2008-09-25 |
United States Patent
Application |
20080230213 |
Kind Code |
A1 |
Roll; Helmut |
September 25, 2008 |
Fully-Metal Heat Exchanger And Method For Its Production
Abstract
The invention relates to a fully-metal heat exchanger comprising
flat tubes (1), which have two narrow sides and two wide sides (2,
3), and comprising fins (4) which form a block together with the
flat tubes, and comprising either at least one tube plate (5) and
one collecting tank (6), with edges (10) of the collecting tank (6)
being connected, for example soldered, to edges (20) of the tube
plate (5), or at least one collecting tank (6) which contains the
tube plate, and having projections (11) which are arranged at
intervals. The invention leads to a heat exchanger which has a
small installation space requirement while having comparatively
good thermal properties in that, according to the invention, the
projections (11) engage in the ends of the flat tubes (1) in the
region of the narrow sides (2). The production method according to
the invention accordingly provides that the projections (11) are
inserted into the ends of the flat tubes (1) approximately in the
region of the narrow sides (2).
Inventors: |
Roll; Helmut; (Bad Urach,
DE) |
Correspondence
Address: |
MICHAEL BEST & FRIEDRICH LLP
100 E WISCONSIN AVENUE, Suite 3300
MILWAUKEE
WI
53202
US
|
Family ID: |
36123144 |
Appl. No.: |
11/916459 |
Filed: |
February 18, 2006 |
PCT Filed: |
February 18, 2006 |
PCT NO: |
PCT/EP2006/001487 |
371 Date: |
May 14, 2008 |
Current U.S.
Class: |
165/173 ;
29/890.03 |
Current CPC
Class: |
F28F 9/001 20130101;
F28F 9/002 20130101; Y10T 29/4935 20150115; F28D 1/05366 20130101;
F28F 9/182 20130101; F28F 2225/08 20130101; F28F 9/185 20130101;
B21D 53/08 20130101; F28F 9/0224 20130101; F28F 2275/04
20130101 |
Class at
Publication: |
165/173 ;
29/890.03 |
International
Class: |
F28F 9/02 20060101
F28F009/02; B21D 53/02 20060101 B21D053/02 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 11, 2005 |
EP |
05012589.7 |
Sep 17, 2005 |
EP |
05020325.6 |
Claims
1. A fully-metal heat exchanger, comprising: a plurality of flat
tubes each having two narrow and two wide sides, fins which,
together with the flat tubes, form a core, a header and a
collecting tank connected to the header, and projections arranged
at intervals, wherein the intervals of the projections correspond
to the intervals of the flat tubes, so that the projections engage
the narrow sides and extend into the ends of the flat tubes to
connect the tubes to at least one of the header and the collecting
tank.
2. The fully-metal heat exchanger as claimed in claim 1, wherein
the flat tubes protrude with their narrow sides beyond the width of
the header, and in the protruding region, the projections engage
into the ends of the flat tubes.
3. The fully-metal heat exchanger as claimed in claim 1, wherein a
header width protrudes beyond the narrow sides of the flat tubes,
and in the protruding region, the projections engage into the ends
of the flat tubes.
4. The fully-metal heat exchanger as claimed in claim 1, wherein
the projections contact the narrow sides of the flat tubes from the
inside, and are soldered there.
5. The fully-metal heat exchanger as claimed in claim 1, wherein
the projections are arranged at the longitudinal edges of the
collecting tank.
6. The fully-metal heat exchanger as claimed in claim 1, wherein
the header has edges, which are bent in at opposite longitudinal
sides, and openings for receiving in each case one flat tube end,
and wherein the openings extending into the bent longitudinal
edges.
7. The fully-metal heat exchanger as claimed in claim 1, wherein
the headers have edges bent only at the two longitudinal sides, so
that said headers can be produced from one sheet-metal strip of any
desired length.
8. The fully-metal heat exchanger as claimed in claim 1, wherein
the collecting tank has open ends.
9. The fully-metal heat exchanger as claimed in claim 8, wherein
the heat exchanger has side parts which extend over the length of
the flat tubes and close the open ends of the collecting tanks.
10. The fully-metal heat exchanger as claimed in claim 1, wherein
the projections are arranged on one of the header and a frame
adjacent to the header.
11. The fully-metal heat exchanger as claimed in claim 1, wherein
the projections are formed on an additional part which extends
along a wall of the collecting tank and is connected thereto.
12. The fully-metal heat exchanger as claimed in claim 1, wherein
the header is integrally formed with the collecting tank, and
wherein the collecting tank has two walls which are bent away from
the header.
13. The fully-metal heat exchanger as claimed in claim 12, wherein
the receiving openings extend into the walls of the collecting
tank.
14. The fully-metal heat exchanger as claimed in claim 11, wherein
the additional part bears externally approximately flat against the
wall of the collecting tank.
15. The fully-metal heat exchanger as claimed in claim 11, wherein
the additional part is provided with retaining functions for
accessories.
16. The fully-metal heat exchanger as claimed in claim 11, wherein
the additional part is provided with a contour which corresponds to
the contour of the wall of the collecting tank.
17. The fully-metal heat exchanger as claimed in claim 11, wherein
the projections are first projections, with the additional part
having second projections between the first projections.
18. The fully-metal heat exchanger as claimed in claim 11, wherein
the additional part is formed at the end with a hook or the like
which is suitable for engaging a side part of the heat
exchanger.
19. The fully-metal heat exchanger as claimed in claim 1, wherein
the projections are contoured to assist their insertion into the
ends of the flat tubes.
20. The fully-metal heat exchanger as claimed in claim 1, wherein
the projections are formed in the manner of incisors.
21. The fully-metal heat exchanger as claimed in claim 1, wherein
the heat exchanger is an air-cooled charge air cooler.
22. A method for producing a fully-metal heat exchanger, the method
comprising the acts of: forming a core from a plurality of flat
tubes and fins; connecting headers to the ends of the flat tubes;
connecting edges of the collecting tanks to edges of the headers,
and inserting projections arranged on a component along narrow
sides of ends of the flat tubes.
23. The method as claimed in claim 22, wherein the projections
extend outwardly from one, of the collecting tank and the header.
Description
TECHNICAL FIELD
[0001] The invention relates to a fully-metal heat exchanger,
composed of flat tubes having two narrow and two wide sides and of
fins which, together with the flat tubes, form a block, and which
fully-metal heat exchanger has either at least one tube base and a
collecting tank, with edges of the collecting tank being connected,
for example soldered, to edges of the tube base, or at least one
collecting tank which contains the tube base, and having
projections which are arranged at intervals. The invention also
relates to a production method for heat exchangers.
PRIOR ART
[0002] The heat exchanger described above is known, for example,
from DE 198 19 247 A1. The projections therein correspond to
openings in the tube bases. In this way, it is provided that the
individual parts are provisionally held together before the
soldering process is carried out. The expenditure for auxiliary
soldering aids can be considerably reduced. A certain disadvantage
of the known heat exchanger is that the tube base still protrudes a
considerable distance beyond the fin/flat-tube block, which could
be considered to be an unnecessary spatial requirement. In
addition, the ratio of the cross sections taken up by the flat
tubes in relation to the overall cross section of the heat
exchanger or of its tube bases is not optimal, so that improvements
are possible with regard to an efficient heat exchanger.
ILLUSTRATION OF THE INVENTION
[0003] The object of the invention is that of providing a heat
exchanger which, while providing comparatively good thermotechnical
values, has a low spatial requirement.
[0004] It is possible as a side effect to expect a
production-friendly, in particular also flexible design.
[0005] The object is achieved according to the invention with
regard to the fully-metal heat exchanger by using the features of
claim 1. The production method according to the invention is the
subject matter of claim 22. It is provided that the projections
engage in the region of the narrow sides into the ends of the flat
tubes. The projections are preferably situated at the opposite
longitudinal edges of the collecting tank.
[0006] Preferably means in this case that embodiments may be
provided in which the projections are arranged at the longitudinal
edges of the tube base, possibly associated with the disadvantage
that the tube bases become more complex and some other advantages
are not provided. Another possible design is to provide a metallic,
frame-like additional part which has the projections.
[0007] The production method leads to several advantages. The
projections, which are inserted into the flat tube ends, at the two
opposite edges of the collecting tank hold the flat tubes under
tension during the subsequent soldering process, so that the risk
of a so-called "falling in" of the flat tubes, with the result of
inadequate soldered connections to the tube base, is significantly
reduced. The invention therefore also permits the use of flat tubes
whose wide sides can have relatively large dimensions, and
accordingly avoids the use, which is complex in production terms,
of a plurality of flat tube rows in the direction of the depth of
the flat-tube/fin block. In other words, it is possible by means of
the invention to provide heat exchangers over a significantly wider
power spectrum with significantly less variation expenditure.
[0008] In addition, the abovementioned advantages of the prior art
are maintained, that is to say in particular the expenditure for
auxiliary soldering aids is considerably reduced, since the
inserted projections assist in holding together the assembled
individual parts of the heat exchanger.
[0009] Because the flat tubes extend over the entire depth of the
tube base--and preferably even beyond this--there is practically no
space which would not be available for the purpose of heat
transfer. In other words, that cross-sectional area of the flat
tubes through which flow passes is in a favorable ratio to the
entire area covered by the tube base, which is in turn
approximately the same as the area in this regard which is covered
by the entire heat exchanger.
[0010] In addition, the proposed heat exchanger has a higher degree
of process reliability during production than heat exchangers which
do not have tube bases but have, instead of the tube bases, widened
flat tube ends, as are known for example from DE 195 43 986 A1 or
from even much earlier documents.
[0011] It is the case either that the flat tubes protrude with
their narrow sides beyond the width of the tube base, and in the
protruding region, the projections engage into the ends of the flat
tubes, or that the tube base width protrudes beyond the narrow
sides of the flat tubes, and in the protruding region, the
projections engage into the ends of the flat tubes.
[0012] The first of said alternatives is, as mentioned, preferable,
because it better prevents the previously mentioned "falling in" of
the flat tubes, since in this case the edge of the collecting tanks
with the projections bear from the outside against the edge of the
tube base, and because, as a result, the projections are
particularly resistant to forces which act in the direction of the
wide side, that is to say transversely with respect to the
longitudinal direction of the flat tubes. In addition, said
alternative also appears to be more favorable with regard to
producing sealed connections.
[0013] The projections in each case make contact with the narrow
sides of the flat tubes from the inside, and are preferably
soldered there.
[0014] The tube base preferably has edges, which are bent in a way
known per se, and openings for receiving in each case one flat tube
end. According to the proposal, however, the openings extend into
the bent edges.
[0015] The tube bases have edges bent only at the two longitudinal
sides, so that said tube bases can be produced from one sheet-metal
strip of any desired length. The tooling costs for changing over to
different heat exchanger sizes are considerably reduced as a
result.
[0016] The collecting tank has end-side openings. Each collecting
tank is therefore constituted by only one metal sheet with two
bends, which is likewise advantageous in production terms.
[0017] The end-side openings of the collecting tank are closed off
by means of side parts, which are known per se, which extend over
the length of the flat tubes.
[0018] The projections are expediently shaped in such a way as to
assist their insertion into the ends of the flat tubes. One
advantageous refinement provides forming the projections in the
manner of incisors. Said design makes it possible to better
compensate length tolerances in the flat tubes. Despite the
unavoidable length tolerances, it is possible to produce sealed
connections between the projections and the flat tube ends.
[0019] The fully-metal heat exchanger can, in the widest sense, be
used to advantage anywhere where there is a requirement for good
heat transfer efficiency with a simultaneously low spatial
requirement. The inventor envisages using heat exchangers of said
type specifically as air-cooled charge-air coolers in motor
vehicles, but without thereby excluding any other possible
application, especially in the field of motor vehicles.
[0020] A fully-metal heat exchanger should be a heat exchanger
whose constituent parts, which are specified in the claims, are
composed of metal, preferably of aluminum, regardless of whether or
not other, non-metal parts which could belong to the system are
subsequently fastened to said heat exchanger. For example,
comparatively complex accessories are to be attached and securely
fastened to fully-metal heat exchangers which are produced from
shaped metal sheets.
[0021] The projections, which are provided on a comb-like
additional part such as a sheet metal strip or the like which is
connected to the wall of the collecting tank, which sit in the flat
tube ends hold the flat tubes under tension during the subsequent
soldering process, so that the risk of the abovementioned "falling
in" of the flat tubes, with the result of inadequate soldered
connections in the receiving openings, is also significantly
reduced by the provision of the additional part. In addition, the
advantages of the prior art are maintained, that is to say in
particular the expenditure for auxiliary soldering aids is
considerably reduced, since the strips (additional parts) have
hooks on the ends which assist in holding the assembled individual
parts of the heat exchanger together by engaging over the side
parts.
[0022] The collecting tanks can be of single-part or multi-part
design. A prominent feature is a part which has a U-shaped cross
section, with the base section being provided with receiving
openings for the tube ends, and the two limbs forming the two walls
of the collecting tank. If the walls are shaped and joined together
to form a space, then single-part collecting tanks are formed. If
the walls remain substantially planar, a second part is required
for forming the closed space, resulting then in two-part collecting
tanks being formed. The receiving openings extend at least into the
walls of the collecting tank.
[0023] Said projections are also expediently shaped so as to assist
their insertion into the ends of the flat tubes.
[0024] The additional part is a chamber-like sheet-metal strip
which in shaping terms is easy to process in order to form the
additional part. Within the context of the present invention, the
term "strip" encompasses all possible physical embodiments, so that
an additional part can be generally referred to thereby. Said
projections on the strip or additional parts can be first
projections for the case that second projections are provided on
the strip. The second projections are then arranged between the
first projections. The second projections improve the assembly or
the preparation of the heat exchanger for the following soldering
process.
[0025] The method according to the invention for producing a
fully-metal heat exchanger, with flat tubes and fins being placed
together to form a flat-tube/fin block, whereafter tube bases are
placed on the ends of the flat tubes and finally collecting tanks
are placed with their edges on the edges of the tube bases, is
characterized in that projections which are arranged on a component
are inserted, in the region of the narrow sides of the flat tubes,
into the ends thereof.
[0026] The longitudinal edges of the collecting tank preferably
bear against the longitudinal edges of the tube base from the
outside. The narrow sides of the flat tubes protrude beyond the
longitudinal edges, so that projections situated at the
longitudinal edges of the collecting tank can be inserted into the
protruding flat tube regions. In this way, the projections hold the
flat tubes in a tensioned state.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] The invention is described in the following in two exemplary
embodiments with reference to the appended drawings.
[0028] FIG. 1 shows an exploded illustration of the heat exchanger
according to the invention;
[0029] FIG. 2 shows a front view;
[0030] FIG. 3 shows a plan view;
[0031] FIGS. 4 and 5 show perspective views of a part of a heat
exchanger;
[0032] FIG. 6 shows a perspective overall view of the heat
exchanger;
[0033] FIG. 7 shows a detail of the flat tube;
[0034] FIGS. 8 and 9 show an alternative embodiment;
[0035] FIG. 10 shows an exploded illustration of the heat exchanger
according to the invention.
[0036] FIGS. 11 and 12 show perspective views of the fully-produced
heat exchanger.
[0037] FIGS. 13 and 14 show perspective views of a part of the heat
exchanger in an assembly situation.
[0038] FIG. 15 shows an advantageous design of the projections.
DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0039] All of the illustrated individual parts of the heat
exchanger are composed of metal, preferably of aluminum or aluminum
alloys, which is expediently coated with a solder layer. The
individual parts, such as flat tubes 1, fins 4, tube bases 5,
collecting tanks 6 and side parts 30, are produced from metal
sheets, though it is not excluded that for example the flat tubes 1
could also be produced as drawn tubes. The flat tubes 1 have an
approximately rectangular cross section, it however being possible
for the narrow sides 2 to also be arched outward slightly. In the
embodiment shown, the inner inserts are situated in the flat tubes
1. The flat tubes 1 are then stacked with fins 4 in order to form a
flat-tube/fin block. Tube bases 5 are placed on the ends of the
flat tubes 1, with the ends of the flat tubes 1 being situated in
openings 21 of the tube bases 5, where a sealed soldered connection
is later formed. The collecting tanks 6 are then placed on,
specifically, as can be seen in particular from FIG. 4, with the
projections 11 at the edges 10 of the collecting tanks 6 thereby
being inserted into those edge regions of the flat tubes 1 which
are formed by the narrow sides 2, which protrude slightly beyond
the edges 20 of the tube base 5, of the flat tubes 1. Preferably
situated at the edge of the openings 21 in the tube bases 5 are rim
holes (not illustrated) which preferably point away from the
collecting tank 6, so that the flat tube ends do not protrude
inward in order to ensure a low loss of pressure of the medium
flowing into the flat tubes 1. Webs 22 are provided between the
openings 21 in the tube bases 5. The webs 22 can be of profiled
design in order to increase their stiffness. Finally, the side
parts 30 are placed on, which side parts 30 at the same time close
off the end-side openings 60 of the collecting tanks 6. For this
purpose, the side parts 30 have, at their ends, in each case one
cup-shaped closure piece which fits into the opening 60. The side
parts 30 are provisionally fixed, and hold the individual parts of
the heat exchanger together, by means of deformable retaining
elements 61 which engage into a slot 62 of the side parts. In said
form, the heat exchanger is substantially prepared for carrying out
the CAB hard soldering process. All the connections are produced in
one working operation in the soldering furnace.
[0040] The shape of the projections 11 is expediently matched to
the contour of the flat tubes 1 which is provided in the region of
the narrow sides 2, so that both the insertion is facilitated and
also sealed soldered connections are provided. Certain production
tolerances are also absorbed in this way. The spacing of the
projections 11 at the edge of the collecting tanks 6 corresponds to
the spacing of the flat tubes 1 in the row or with the height of
the fins 4 arranged between the flat tubes 1. Here, certain
tolerances must be permissible which can however be compensated by
the expedient shape of the projections 11 (see the description of
FIGS. 15 and 16 further below).
[0041] The collecting tanks 6 are of particularly
production-friendly, simple configuration. Only two bends are
necessary in order to form the two longitudinal walls and a
transverse wall. Connecting pipes 70, for example, can be easily
produced by means of shaping processes.
[0042] Particularly production-friendly tube bases 5 are also to be
used, which are manufactured from endless band and need merely be
cut to the appropriate length, because said tube bases do not have
any bent edges at their end sides. Accordingly, no expensive
drawing tools are required. It is expedient to make reference here
to FIGS. 4 and 5. It can be seen in said figures that a lug 100,
which is comparable to the projections 11, is provided at the edge
10 of the collecting tank 6. Said lug 100 interacts with the
corresponding cut-out 101 at the edge 20 of the tube base 5 and
ensures sealed soldered connections there. It can also be seen from
FIG. 5 that the openings 21 in the tube base 5 extend into the edge
20, as indicated by the reference symbol 22. The tube bases 5 can
therefore, during assembly, also be pushed transversely with
respect to their longitudinal direction, or in the direction of the
wide sides 3 of the flat tube ends, onto said flat tube ends. In
the prior art, a movement in the longitudinal direction of the flat
tubes is required for this purpose. This is referred to as "drawing
on" the tube bases.
[0043] FIGS. 3 and 6 in particular show, in a view of one of the
side parts 30, that there are no lateral protrusions of the tube
bases 5 beyond the flat-tube/fin block. The width of the side parts
30 corresponds approximately to the dimension of the wide sides 3
of the flat tubes 1.
[0044] It is also to be pointed out that the heat exchanger
according to the invention permits relatively easy access from the
outside to connections which are critical in soldering terms.
Critical connections of said type are the flat-tube/tube-base
connections. Should leakages be present there after the soldering
process is carried out, the corresponding points can, by virtue of
being largely accessible, be easily aftertreated and eliminated in
a second soldering process. In heat exchangers of the prior art, it
is often not possible to do this, resulting in high rejection
rates.
[0045] FIG. 7 schematically shows one individual flat tube 1,
specifically in a view of the flat tube end. Flat tubes 1 of said
type are provided in desired numbers in the heat exchanger. Two
projections 11 extend into each flat tube 1. The penetration depth
need only be a few millimeters; 10-15 mm is more than enough. It
would practically be even less. It is self-evident that the one
projection 11 is situated on the one edge of the collecting tank 6
and the other projection 11 is situated on the opposite, other edge
10 of the collecting tank 6. The projections 11 bear tightly from
the inside against the narrow sides 2 of the flat tubes 1. Situated
in the flat tubes 1 is an inner insert 80, as is typical in
particular for charge air coolers which are impinged on by cooling
air. In other applications, an inner insert is dispensed with
entirely. It is practically often difficult to insert the inner
inserts 80 into the flat tubes 1 in such a way that the least
possible bypass is generated in the region of the narrow sides 2
for the charge air flowing through, which has an adverse effect on
the heat transfer. As shown in FIG. 7, the projections 11 have a
favorable effect on the reduction of the disadvantageous bypass,
which is a further advantage of the invention. The small gaps in
the corners of the flat tubes 1 are caused by the illustration.
They are in practice not present or are securely closed off in the
soldering process. Said gaps will also level out as the projections
11 are inserted, since the projections 11 hold the two wide sides 3
under a certain tension in the direction of the arrow.
[0046] FIGS. 8 and 9 now show an alternative design in which the
projections 11 are arranged on the tube bases 5. In said case, the
tube bases 5 must be drawn on in the tube longitudinal direction,
with the projections 11 simultaneously being inserted into the flat
tube ends 1. Thereafter, the collecting tanks 6 and the side parts
30 are placed on and mounted.
[0047] Single-part collecting tanks 6 have been provided at least
in the exemplary embodiment which is shown in FIGS. 10-14. It is
however provided in any case that the collecting tanks 6 also
comprise the tube bases 5, so that therefore no classic tube bases
are provided as separate parts, as can be gathered from said
figures. The collecting tank 6 has a base section 106 from which
extend two bent walls 107 of the collecting tank 6. The walls 107
are shaped and can be connected by means of a longitudinal weld
seam (not shown) in order to form the collecting tank 6. Provided
in the base section 106 are receiving openings 21 for the flat tube
ends, wherein the spacings of the flat tubes 1 should accordingly
correspond to the spacings of the receiving openings 21. A very
prominent feature is that the receiving openings 21 extend into the
walls 107, that is to say they extend slightly beyond the bent edge
of the walls 107 on the base section 106, as can be seen
sufficiently clearly from FIG. 14 at reference symbol 22. In the
exemplary embodiments shown, in each case one strip (additional
part) 110 is situated on all the walls 107 of the two collecting
tanks 6. At the walls 107 of the one collecting tank 6, the strips
110 have been formed with additional functions such as for example
with retaining functions 90 for accessories (not illustrated). It
is not strictly necessary to provide strips 110 on all the walls
107. It is advantageous to provide a trip 110 in particular
whenever additional functions 70 are to be carried out. In the
present exemplary embodiment, it would be fundamentally entirely
possible to dispense with those narrow strips 110 at the walls 107
of the left-hand collecting tank 6 which do not provide any
additional function, and for this purpose to provide there the
solution described above, that is to say, there, the projections 11
would be arranged directly on the walls 107 of the collecting tank
6, and tube bases would be provided as individual parts, as shown
in the figures.
[0048] A further advantage of the strip 110 can be gathered from
FIG. 12. It can be seen in said figure that the strip 110, which is
formed with the stated additional functions, can also contribute to
the strength of the collecting tank 6. It can be seen in FIG. 12
that the strip 110 extends over a considerable part of the wall 107
of the collecting tank and is soldered to said wall 107.
[0049] It is possible from FIGS. 13 and 14 to more clearly see the
design of the strip 110 with regard to the projections 11 which are
arranged thereon at intervals. The projections 11 can be provided
with a contour which serves to facilitate the sliding of said
projections 11 into the flat tubes 1. Between the projections 11,
which are first projections 11, are situated in each case second
projections 12. As can be seen, in each case one second projection
12 has been arranged between two first projections 11. The second
projections 12 cause a counteracting moment of the strip 110 which
could otherwise, when the first projections 11 are situated in the
flat tube ends, seek to stick out away from the wall 107, which is
undesirable. Since the second projections 12 bear in each case
against the fins 4 from the outside, this is prevented or at least
counteracted.
[0050] It can also be seen from FIGS. 13 and 14 that it is
advantageous to form a hook 13 at the ends of the strip 110, which
hook 13 is suitable to fixedly hold the side part 30 against the
outer fin 4. This assists in holding the entire heat exchanger
together before soldering. In addition, this also suppresses the
abovementioned "sticking out" of the strip 110 from the wall 107.
In addition, it is also possible in this way to dispense with the
brackets, shown in FIG. 1 at positions 61 and 62, which are
intended to retain the side parts 30 in the end-side openings 60 of
the collecting tank 6, which is also advantageous in production
terms.
[0051] FIG. 15 shows a detail with only one projection 11. The
projections 11 have been designed in the manner of incisors 111.
Length tolerances in the flat tubes which are in the range from
+/-1.0 mm can be better absorbed in this way. Sharp edges 112 have
been formed on said projections 11, which sharp edges 112 also
extend in the radii, that is to say in the region of the transition
from the projection 11 into the wall of the collecting tank 6 or of
the additional part or of the tube base. As the projections 11 are
inserted into the flat tube ends, the sharp edges 112 cut said ends
of those flat tubes which are in the upper length tolerance range
open slightly and "crumple" said ends around slightly. This can be
clearly seen in FIG. 16 at k. The central tube there is slightly
longer than the two other tubes. The sharp edge of the projection
11 is produced for example by means of cold shaping. The thickness
difference between the projections 11 and the wall of the flat
tubes assists said process. The wall of the collecting tank 6, from
which the projections 11 are for example formed, can be
approximately 1.0-2.0 mm thick, while the thickness of the wall of
the flat tubes can be in the range from 0.05-0.25 mm.
[0052] Overall, the invention accordingly provides an innovative
product which, compared to the prior art, leaves little to be
desired.
* * * * *