Note: Descriptions are shown in the official language in which they were submitted.
i t
2193933
1
TITLE OF THE INVENTION
PROCESS FOR PRODUCING FLAT HEAT EXCHANGE TUBES
BACKGROUND OF THE INVENTION
The present invention relates to a process for
producing flat heat exchange tubes, more particularly
to flat heat exchange tubes for condensers, evaporators
and like heat exchangers for use in car coolers.
JP-B No. 45300/91 discloses a condenser for use in
car coolers which comprises a pair of headers arranged
at right and left in parallel and spaced apart from
each other, parallel flat heat exchange tubes each
joined at its opposite ends to the two headers,
corrugated fins arranged in an air flow clearance
between adjacent heat exchange tubes and brazed to the
adjacent tubes, an inlet pipe connected to the upper
end of the left header, an outlet pipe connected to the
lower end of the right header, a left partition
provided inside the left header and positioned above
the midportion thereof, and a right partition provided
inside the right header and positioned below the
midportion thereof, the number of heat exchange tubes
between the inlet pipe and the left partition, the
number of heat exchange tubes between the left
partition and the right partition and the number of
r
21~39~3
2
heat exchange tubes between the right partition and the
outlet pipe decreasing from above downward. A
refrigerant flowing into the inlet pipe in a vapor
phase flows zigzag through the condenser before flowing
out from the outlet pipe in a liquid phase. Condensers
of the construction described are called parallel flow
or multiflow condensers, realize high efficiencies,
lower pressure losses and supercompactness and are in
wide use in recent years in place of conventional
serpentine condensers.
It is required that the heat exchange tube for use
in the condenser have pressure resistance since the
refrigerant is introduced thereinto in the form of a
gas of high pressure. To meet this requirement and to
achieve a high heat exchange efficiency, the heat
exchange tube is made of a hollow aluminum extrudate
which comprises flat upper and lower walls, and a
reinforcing wall connected between the upper and lower
walls and extending longitudinally. To improve the
heat exchange efficiency and to compact the condenser,
it is desired that the flat heat exchange tube have a
small wall thickness and the lowest possible height.
In the case pf extrudates, however, the extrusion
technique imposes limitations on the reduction in the
height of the tube and in the wall thickness.
a
2193933
3
To overcome this problem, U.S. Patent No.
5,553,377 discloses a method of producing a flat heat
exchange tube which comprises a flat metal tube having
parallel refrigerant passages in its interior and
comprising flat upper and lower walls and a plurality
of reinforcing walls connected between the upper and
lower walls, extending longitudinally of the tube and
spaced apart from one another by a predetermined
distance. The known method comprises rolling a metal
sheet blank having a thickness greater than the wall
thickness of the heat exchange tube to be produced with
a pair of upper and lower rolling rolls one of which
has parallel annular grooves and thereby reducing the
thickness of the blank to the specified tube wall
thickness with the peripheral surfaces of the rolling
rolls to form a flat portion serving as at least one of
the upper wall and the lower wall and form vertical
ridges projecting from the flat portion integrally
therewith and providing the reinforcing walls with the
annular grooves.
However, the method described has the problem of
using production equipment which is large-sized in its
entirety since the metal sheet blank needs to be passed
through a plurality of rolling mills.
An object of the present invention is to provide a
CA 02193933 2004-11-26
25088-154
4
process for producing flat heat exchange tubes by
production equipment which can be compacted in its
entirety.
SUMMARY OF THE INVENTION
The present invention provides a process for
producing a flat heat exchange tube having parallel
refrigerant passages in its interior and comprising
flat upper and lower walls to which fins are to be
joined, and a plurality of reinforcing walls connected
between the upper and lower walls, extending
longitudinally of the tube and spaced apart from one
another by a predetermined distance, using a rolling
mill comprising a central work roll and a plurality of
planetary work rolls arranged around a portion of the
periphery of the central work roll and spaced apart
circumferentially thereof, the central work roll or the
planetary work rolls being formed with parallel annular
grooves in the periphery of the roll, the process
comprising rolling a metal sheet blank by the rolling
mill and thereby reducing the thickness of the blank to
a specified value with the peripheral surface of the
central work roll and the peripheral surfaces of the
planetary work rolls to form a flat portion serving as
at least one of the upper wall and the lower wall and
form vertical ridges projecting from the flat portion
7 I
2193933
integrally therewith and providing the reinforcing
walls with the annular grooves. Thus, the single
rolling mill produces a rolled metal sheet comprising a
flat portion providing at least one of the upper wall
5 and the lower wall, and vertical ridges integral with
the flat portion and providing the reinforcing walls.
Preferably, the rolling mill has a guide shoe
between each pair of immediately adjacent planetary
work rolls, and means for biasing the guide shoe toward
the central work roll. This suppresses longitudinal
elongation of the metal sheet blank while the blank
passes through the rolling mill, further inhibiting the
blank from bulging between the adjacent planetary work
rolls. Consequently, the work roll or rolls having the
parallel annular grooves give the rolled metal sheet a
specified cross sectional configuration. To obtain the
rolled metal sheet of the specified cross sectional
configuration reliably, it is desired to arrange the
plurality of planetary work rolls relative to the
central work roll so that the rolling clearance
gradually decreases toward the direction of advance of
the metal sheet blank.
It is also desired that a roll formed with
parallel annular grooves and parallel shallow annular
grooves between each two adjacent annular grooves be
~'~ ~39~3
6
used as the central work roll or as each of the
planetary work rolls to form heat transfer area
increasing low ridges projecting from the flat portion
integrally therewith when forming the vertical ridges
projecting from the flat portion integrally therewith
and providing the reinforcing walls with the annular
grooves.
It is also desired that a roll formed with
parallel annular grooves and projections provided at a
predetermined interval in each of the grooves and
having a height smaller than the depth of the groove be
used as the central work roll or as each of the
planetary work rolls, whereby when the vertical ridges
projecting from the flat portion integrally therewith
and providing the reinforcing walls are formed with the
annular grooves, a plurality of cutouts are formed at
the predetermined interval in the upper edge of each of
the ridges for forming holes for effecting
communication between the parallel refrigerant
passages.
The communication holes in the reinforcing walls
permit the refrigerant flowing through the parallel
refrigerant passages to flow also widthwise of the flat
heat exchange tube, whereby portions of the refrigerant
are so mixed together as to eliminate refrigerant
2193933
temperature differences between the passages. The
opening ratio which is the percentage of all the
communication holes in each reinforcing wall to the
wall is preferably 10 to 40~. When in this range, the
opening ratio assures satisfactory thermal conductance,
assuring the heat exchange tube of a greatly improved
heat exchange efficiency. If the ratio is less than
10~, the thermal conductance does not increase, whereas
even when the ratio exceeds 40~, the conductance no
longer increases but only an increased coefficient of
friction will result. The opening ratio within the
range of 10 to 40~ is more preferably l0 to 30~, most
preferably about 20~.
The communication holes are so sized in cross
section as to permit the refrigerant to smoothly flow
therethrough between the adjacent passages, to be free
of the likelihood of becoming clogged with a flow of
solder during brazing and not to impair the pressure
resistance of the heat exchange tube. The pitch of the
communication holes is such that the holes will not
lower the pressure resistance of the tube while
permitting the refrigerant to smoothly flow across the
reinforcing walls. The communication holes formed in
the plurality of reinforcing walls are preferably in a-
staggered arrangement when seen from above.
2193933
8
The pitch of the reinforcing walls in the
widthwise direction of the tube is preferably up to 4
mm. A lower heat exchange efficiency will result if
the pitch is in excess of 4 mm. The height of the
reinforcing walls is preferably up to 2 mm. If the
wall height is over 2 mm, not only difficulty is
encountered in fabricating a compacted heat exchanger,
but the resistance to the passage of air also increases
to result in an impaired heat exchange efficiency.
The present invention will be described in greater
detail with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross sectional view of a flat heat
exchange tube produced by the process of Embodiment 1
of the invention;
FIG. 2 is an enlarged fragmentary view in cross
section of the flat heat exchanger tube of FIG. 1:
FIG. 3 is an enlarged view in section taken along
the line 3-3 in FIG. 1~
FIG. 4 is a diagram schematically showing an
apparatus for producing a lower member for composing
the tube of FIG. 1;
FIG. 5 us an enlarged view in section taken along
the line 5-5 in FIG. 4~
FIG. 6 is an enlarged fragmentary perspective view
CA 02193933 2004-11-26
25088-154
9
in cross section showing in development the peripheral
surface of a central roll included in the apparatus of
FIG. 4;
FIG. 7 is a cross sectional view of the lower
member for composing the tube of FIG. 1;
FIG.11 is an enlarged fragmentary perspective view
showing how the lower component member and an upper
component member are joined by the process of
Embodiment 1;
FIG.12 is an enlarged perspective view in cross
section of an aluminum sheet.blank prerolled by a
prerolling mill of the apparatus of FiG. 4;
FIG. 8 is a cross sectional view showing the
upper component member as fitted to the lower component
member by the process of Embodiment 1;
FIG. 13 is a perspective view showing a device for
temporarily attaching the upper component member to the
lower component member in the process of Embodiment 1;
FIG. 9 is a cross sectional view of a flat heat
exchange tube produced by the process of Embodiment 2
of the invention;
FIG. 14 is an enlarged fragmentary view in cross
section of the flat heat exchanger tube of FIG. 9;
FIG. 18 is an enlarged fragmentary perspective
view showing how an upper component member and a lower
CA 02193933 2004-11-26
25088-154
' 10
component member are joined by the process of
Embodiment 2;
FIG. 10 is a cross sectional view showing the
upper component member as fitted to the lower component
member by the process of Embodiment 2~
FIG. 15 is a cross sectional view of a flat heat
exchange tube produced by the process of Embodiment 3
of the invention;
FIG. 19 is a cross sectional perspective view of a
member for composing the tube of FIG. 15;
FIG. 20 is a sectional view corresponding to FIG.
5 and showing a finishing rolling mill for preparing
the component member of FIG. 19;
FIG. 16 is a cross sectional view of a flat heat
exchange tube produced by the process of Embodiment 4
of the invention:
FIG. 21 is a cross sectional perspective view of a
member for composing the tube of FIG. 16;
FIG. 17 is a cross sectional view of a flat heat
exchanger tube produced by the process of Embodiment 5
of the invention;
FIG. 22 is a cross sectional perspective view of a
member for composing the tube of FIG. 21;
FIG 23 is a cross sectional view of a flat heat
exchanger tube produced by the process of Embodiment 6
11
of the invention;
FIG. 24 is a cross sectional perspective view
showing how to join an upper component member and a
lower component member by the process of Embodiment 6;
and
FIG. 25 is a front view of a condenser comprising
flat heat exchange tubes of the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Embodiments of the present invention will be
described below with reference to the drawings. The
term "aluminum" as used in the following description
includes pure aluminum and aluminum alloys. Throughout
the drawings, like parts are designated by like
reference numerals and will not be described
repeatedly.
FIG. 25 shows a condenser comprising flat heat
exchange tubes embodying the invention. The condenser
comprises a pair of headers 121, 122 arranged at right
and left in parallel and spaced apart from each other,
parallel flat heat exchange tubes 123 each joined at
its opposite ends to the two headers 121, 122,
corrugated fins 124 arranged in an air flow clearance
between adjacent heat exchange tubes 123 and brazed to
the adjacent tubes 123, an inlet pipe 125 connected to
the upper end of the left header 121, an outlet pipe
~:g~.3
12
126 connected to the lower end of the right header 122,
a left partition 127 provided inside the left header
121 and positioned above the midportion thereof, and a
right partition 128 provided inside the right header
122 and positioned below the midportion thereof, the
number of heat exchange tubes 123 between the inlet
pipe 125 and the left partition 127, the number of heat
exchange tubes 123 between the left partition 127 and
the right partition 128 and the number of heat exchange
tubes 123 between the right partition 128 and the
outlet pipe 126 decreasing from above downward. A
refrigerant flowing into the inlet pipe 125 in a vapor
phase flows zigzag through the condenser before flowing
out from the outlet pipe 126 in a liquid phase.
The flat heat exchange tubes in the above
condenser are those embodying the invention. Examples
of flat heat exchange tubes embodying the invention
will be described below. In the following embodiments,
all reinforcing walls are 10 to 40~ in opening ratio
which is the percentage of all communication holes
formed in the reinforcing wall based on the wall. The
communication holes formed in a plurality of
reinforcing walls are all in a staggered arrangement
when seen from above. The article to be brazed is
degreased before brazing and thereafter coated with a
CA 02193933 2004-11-26
25088-154
13
brazing flux.
Embodiment l
This embodiment is shown in FIGS. 1 to 8 and 11 to 13.
The process of this embodiment produces a flat heat
exchange tube A, which as shown in FIGS. 1 to 3,
comprises flat upper and lower walls 1, 2 to which fins
are to be brased, vertical left and right side walls 3,
4 connected between opposite side edges of the walls 1,
2, and a plurality of reinforcing walls 5 arranged
between the side walls 3, 4, connected between the
upper and lower walls 1, 2, extending longitudinally of
the tube A and spaced apart from one another by a
predetermined distance. The tube A has parallel
refrigerant passages 6 in its interior. Between the
adjacent reinforcing walls 5, heat transfer area
increasing low ridges 7 are formed on the upper surface
of the lower wall 2 integrally therewith. A plurality
of trapezoidal communication holes 8 are formed in the
upper end of each wall 5 for effecting communication
between the parallel refrigerant passages 6.
The flat heat exchange tube A comprises an upper
component member 20 in the form of.a flat plate and
providing the upper wall 1, and a lower component
member 10 comb-shaped in cross section and having a
flat portion 11 providing the lower wall 2, right and
~~ ~~9~3
14
left upright portions 12 providing right and left side
walls 4, 3, ridges 13 providing the reinforcing walls
5, and the heat transfer area increasing low ridges 7.
Each upright portion 12 of the lower component member
10 has a stepped part 12a at the same level as the
upper end of the ridge 13, and a thin wall 15 extending
upward from the stepped part. The upper component
member 20 has a slope 21 slanting outwardly downward
and providing an upper surface at each of its opposite
side portions. The upward thin wall 15 is to be fitted
over the slope 21 by being bent. Each ridge 13 has
trapezoidal cutouts 14 providing the communication
holes 8.
The flat heat exchange tube A is produced by the
following process.
First, the lower component member 10 shown in
FIGS. 7 and 8 is prepared using the apparatus shown in
FIGS. 4 to 6.
With reference to FIG. 4, the apparatus for
preparing the lower component member 10 comprises an
uncoiler 31 having an aluminum sheet blank 30 (in the
form of an aluminum brazing sheet with a brazing
material layer on one surface thereof) rolled up
thereon with the brazing material layer positioned
outside, a preliminary rolling mill 32, a finishing
CA 02193933 2004-11-26
25088-154
rolling mill 33 and transport rolls 34. The aluminum
sheet blank 30 is paid out from the uncoiler 31, passed
through the preliminary rolling mill 32, thereafter fed
to the finishing rolling mill 33 and thereby rolled for
5 finishing, whereby the lower component member 10 is
prepared.
As shown in FIG. 12, the preliminary rolling mill
32 causes one side of the aluminum sheet blank 30
opposite to the brazing material layer to project and
10 forms thick wall portions 30a at its opposite side edge
portions.
The finishing rolling mill 33 comprises a central
work roll 35, and a plurality of planetary work rolls
36 arranged around a portion of the periphery of the
15 roll 35 thereabove and equidistantly spaced apart
circumferentially of the roll 35. The planetary work
rolls 36 are arranged relative to the central work roll
35 so that the rolling clearance gradually decreases
toward the direction of advance of the aluminum sheet
blank 30.
The central work roll 35 is rotated by
unillustrated drive means. The planetary work rolls 36
are rotatable with the central work roll 35 by an
unillustrated gear device, such that the rotation of
the roll 35 rotates all the planetary work rolls 36 at
~ 193933
16
the same peripheral speed as the roll 35. The
finishing rolling mill 33 further has a trapezoidal
guide shoe 37 between each pair of immediately adjacent
planetary work rolls 36, and springs 38 for biasing the
guide shoe 37 toward the central work roll 35. Each of
the front and rear edges of the guide shoe 37 extends
into the clearance between the roll 35 and the roll 36
to such an extent that the shoe will not contact these
rolls. The guide shoes 37 suppress the longitudinal
10- elongation of the aluminum sheet blank 30 while the
blank 30 passes through the mill 33, further inhibiting
the blank from bulging outward between the adjacent
planetary work rolls 36. The longitudinal elongation
of the blank 30 is suppressed also by rotating all the
_ planetary rolls 36 at the same peripheral speed as the
central roll 35. Since the longitudinal elongation of
the aluminum sheet blank 30 is suppressed, the blank
can be of a smaller thickness than the aluminum sheet
conventionally used. This decreases the material cost,
and the rolling reduction can be smaller than in the
prior art.
With reference to FIGS. 5 and 6, the central work
roll 35 of the finishing rolling mill 33 is formed in
its peripheral surface with parallel annular grooves
39, 40 which are equal in depth, and trapezoidal
CA 021193933 2004-11-26
25088-154
1?
projections 43 are formed at a predetermined interval
in each of the annular grooves 40 other than the
annular grooves 43 at the opposite ends, the
projections 43 having a height smaller than the depth
of the grooves 40. The annular groove 39 at each of
the opposite ends has a larger width than the other
grooves 40 and is further formed with an annular groove
41 of small width at the outer edge of its bottom.
Parallel shallow annular grooves 42 are further formed
in the roll 35 between each pair of immediately
adjacent annular grooves 39, 40.
The aluminum sheet blank 30 shown in FIG. 12 and
formed with the thick wall side portions 30a and a thin
wall portion 30b therebetween is rolled by being passed
between the central work roll 35 and the planetary work
rolls 36. As shown in FIG. 7, the rolling operation
thins the blank 30 to a predetermined thickness,
forming a flat portion 11 providing the lower wall 2,
and causes the annular grooves 39, 40 to form upright
portions 12 providing right and left side walls 3, 4
and vertical ridges 13 providing the reinforcing walls
5, these portions 12, 13 projecting from the flat
portion integrally therewith. Furthermore, the
projections 43 in each groove 40 form trapezoidal
cutouts 14 in the upper end of the ridge 13 at a
CA 02193933 2004-11-26
25088-154
18
predetermined interval, and the grooves 42 form heat
transfer area increasing ridges 7 similarly projecting
from the flat portion 11 integrally therewith. The
annular grooves 41 of small width form, at the upper
parts of the upright portions 12 of greater thickness
than the ridges 13, stepped parts 12a at the same level
as the upper ends of the ridges 13 and an upward thin
wall 15 extending from each stepped part 12a.
It is now assumed that the lower component member
10 shown in FIG. 7 and to be prepared is 18 mm in
overall width W, 0.35 mm in the wall thickness T of the
flat portion 11, 1 mm in the height H of the upright
portions 12, 1.4 mm in the thickness T1 thereof, 0.65
mm in the height H1 of the upward thin walls 15, 0.4~mm
in the thickness T2 thereof, 1 mm in the height H2 of
the ridges 13, 0.4 mm in the thickness T3 thereof, 0.8
mm in the pitch P of the ridges 13, 0.2 mm in the
height H3 of the low projections 7 and 0.2 mm in the
thickness T4 thereof. In this case, suppose the
aluminum sheet blank 30 shown in FIG. 12 is w in width,
wl in the width of the thick wall portions 30a, t in
the thickness of the thin wall portion 30b and tl in
the thickness of the thick wall portions 30a. The
lower component member 10 can then be prepared with the
above design dimensions when w=18 mm, wl=1.34 mm,
CA 02193933 2004-11-26
25088-154
19
t=0.57 mm and tl=1.13 mm, when w=18 mm, wl=1.49 mm,
t=0.62 mm and tl=1.19 mm, and when w=18 mm, wl=1.63 mm,
t=0.68 mm and t=1.25 mm.
The aluminum sheet blank 30 of FIG. 12 has the
thick wall portions 30a which are formed by causing one
side of the blank opposite to the brazing material
layer to project, whereas the brazing material layer
side may conversely be caused to project, or both sides
may be caused to project to form the thick portions.
Separately from the lower component member 10, the
upper component member 20 is prepared from a flat
aluminum sheet which is in the form of an aluminum
brazing sheet covered with a brazing material layer
over opposite sides thereof and which is formed with a
slope 21 slanting outwardly downward on the upper
surface of each side edge portion thereof (see FIG.
11). The upper member 20 is temporarily attached to the
lower member 10 by placing each side edge portion of
the upper member 20 on the stepped part a of the
upright portion 12 of the lower member 10, inwardly
bending the upward thin wall 15 of each upright portion
12 and thereby intimately fitting the wall 15 over the
slope 21 of the upper member 20. This operation is
continuously conducted using a device which comprising
pairs of upper and lower forming rolls 80 for bending
CA 02193933 2004-11-26
25088-154
the thin walls 15, and pairs of upper and lower pinch
rolls 81 for nipping the upper and lower component
members 20, 10 from above and below as seen in FIG. 13.
Subsequently, the temporarily secured assembly is
5 cut into specified lengths by a shear to obtain
intermediate products of heat exchange tubes. The
assembly is thus cut in the direction of height of the
product, i.e., from above or below. This prevents the
upright portions 12 and the ridges 13 from deforming.
10 These portions are likely to deform if the assembly is
cut widthwise of the product; i.e., from the right or
left.
Such intermediate products of heat exchange tubes
are collectively brazed in combination with. the headers
15 and tins. By this procedure, the upper member 20
placed over the ridges 13 is made to provide the upper
wall 1 of a flat heat exchange tube A, the bent upward
thin walls 15 of the upper member 20 are brazed to the
stepped parts a of the respective upright portions 12
20 of the lower member 10 to make the upright portions 12
serve as the right and left side walls 4, 3, the ridges
13 of the lower wall 2 are brazed to the upper wall 1
to form the reinforcing walls 5, and the openings of
the trapezoidal cutouts 14 in the ridges 13 are closed
with the upper wall 1 to thereby form the trapezoidal
CA 02193933 2004-11-26
25088-154
21
communication holes 8 for holding the parallel
refrigerant passages 6 in communication with one
another. In this way the flat heat exchange tube A is
obtained.
The assembly of the upper and lower members 20, 10
as temporarily secured may be temporarily joined as by
high-frequency brazing before the above brazing
procedure. Alternatively the upper and lower members
20, 10 as temporarily attached to each other may be
brazed to obtain a finished product of heat exchange
tube. The headers and fins may then be brazed to such
tubes to assemble a heat exchanger.
Embodiment 2
This embodiment is shown in FIGS. 9, 10, 14 and 18.
The process of this embodiment provides a flat
heat exchange tube A1 which has the same construction
as the tube afforded by Embodiment 1 except that right
and left side walls 51, 50 have a double structure as
seen in FIGS. 9 and 14.
The flat heat exchange tube A1, which comprises a
lower component member 60 and an upper component member
70, has the same construction as the tube of Embodiment
1 with the exeption of the following features. The
lower component member 60 has right and left upright
portions 61 having the same height and same thickness
CA OI2193933 2004-11-26
25088-154
. 22
as ridges 5, and is formed at each side edge lower part
of a flat portion 11 with a slope 62 slanting outwardly
upward. The upper component member 70 is formed at
each side edge thereof with a depending portion 72
having approximately the same thickness as the upright
portion 61 and tapered downwardly inward in cross
section at its lower end so that the lower end can be
fitted over the slope 62 by being bent. The upper
member 70 has such a width that the depending portions
72 can be fitted to the respective upright portions 61
of the lower member 60 from outside.
The tube A1 is prepared by the following process.
The lower component member 60 is first formed
using the same apparatus as shown in FIGS. 4 and 5 and
as used for practing the process of Embodiment 1 with
the exception of the following (see FIG. 18),
The apparatus for the present embodiment is not
provided with the preliminary rolling mill 32.
Accordingly, a flat aluminum sheet blank in the form of
a brazing sheet having a brazing material layer on one
side thereof is fed to the finishing rolling mill 33.
The central work roll 35 of the finishing rolling mill
33 is formed in its peripheral wall with parallel
annular grooves which are all equal in width and depth
except that only the annular grooves at opposite ends
CA 02193933 2004-11-26
25088-154
23
each have a bottom face connected to an outer side face
by a slope.
Separately from the lower component member 60, the
upper component member 70 is prepared from an aluminum
sheet which is in the form of an aluminum brazing sheet
covered with a brazing material layer over opposite
sides thereof and which has depending portions 72 at
its opposite side edges. The depending portions 72
have a slightly greater height than the upright
portions 61 and each have a lower end 73 tapered
downwardly inward in cross section.
Subsequently, the upper member 70 is fitted over
the lower member 60, and the lower ends 73 of the
depending portions 72 of the upper member 70 are bent
inward and thereby intimately fitted to the slopes 62
of the lower member 60, whereby the two members 60, 70
are temporarily joined. The same procedure as in
Embodiment 1 is thereafter performed to obtain a flat
heat exchange tube A1.
Embodiment 3
This embodiment is shown in FIGS. 15, 19 and 20.
As shown in FIG. 15, the process of this
embodiment produces a flat heat exchange tube A2, which
comprises flat upper and lower walls 86, 87 to which
fins are to be brazed, left and right side walls 85, 88
CA 02193933 2004-11-26
25088-154
' 24
each having a circular-arc outer surface and connected
between opposite side edges of the walls 86, 87, and a
plurality of reinforcing walls 89 arranged between the
side walls 85, 88, connected between the upper and
lower walls 86, 87, extending longitudinally of the
tube A2 and spaced apart from one another by a
predetermined distance. The tube A2 has parallel
refrigerant passages 74 in its interior. Each
reinforcing wall 89 is formed at the midportion of its
height with hexagonal communication holes 90 for
holding the parallel refrigerant passages 74 in
communication with one another.
The tube A2 is formed by a single component member
94. As seen in FIG. 19, the component member 94
comprises a central flat portion 92 positioned in the
middle of its width and providing the right side wall
88; a right flat portion 91 providing the upper wall
86, projections 89a providing the upper halves of the
reinforcing walls 89 and a circular-arc portion 85a
providing the upper half of the left side wall 85, the
portions 91, 89a and 85a being positioned at the right
side of the central flat portion 92; and a left flat
portion 93 providing the lower wall 87, projections 89b
providing the lower halves of the reinforcing walls 89
and a circular-arc portion 85b providing the lower
CA 021193933 2004-11-26
25088-154
' 25
half of the left side wall 85, the portions 93, 89b and
85b being positioned at the left side of the central
flat portion 92. Each projection 89a (89b) has
trapezoidal cutouts 90a (90b) for forming the upper
halves (lower halves) of the communication holes 90.
The flat heat exchange tube A2 is prepared by the
following process.
First, the upper component 94 is prepared using
the same apparatus as shown in FIGS. 4 and 5 and as
used for practicing the process of Embodiment 1.
The apparatus for the present embodiment is not
provided with the preliminary rolling mill 32.
Accordingly, a flat aluminum sheet blank in the form of
a brazing sheet having a brazing material layer over
one side thereof is fed to the finishing rolling mill
33. As shown in FIG. 20, the central work roll 35 of
the finishing rolling mill 33 is formed in its
periphery with parallel annular grooves 97 on opposite
sides of the midportion of its length symmetrically,
and projections 99 having a height smaller than the
depth of the grooves are formed at a predetermined
interval in each of the annular grooves 97. At the
right of the outermost right annular groove 97, the
roll 35 has a right-end annular groove 95 greater than
the groove 97 in depth and width and defined by a
2193933
26
bottom face and a vertical inner side face connected
thereto by a slope. At the left of the outermost left
annular groove 97, the roll 35 has a left-end annular
groove 95 greater than the groove 97 in depth and width
and having a slanting bottom face, the upper end of
which is connected to a vertical outer side face by a
stepped portion. The planetary work roll 36 is
provided at its right end with a right flange 98a
having a periphery in contact with the bottom face of
the right-end groove 95, and at the left end thereof
with a left flange 98b having a periphery in contact
with the stepped portion of the left-end groove 96.
The flanges 98a, 98b each have an inwardly curved inner
face.
An aluminum sheet blank 30 is rolled by the mill
33 comprising the central work roll 35 and planetary
work rolls 36 to thin the blank 30 to a predetermined
tube wall thickness with the peripheral surface of the
central work roll 35 and those of the planetary work
rolls 35 to form a central flat portion 92, right flat
portion 91 and left flat portion 93, cause the parallel
annular grooves 97 to form projections 89a, 89b
projecting from the flat portions 91, 93 integrally
therewith, cause the projections 99 in the grooves 97
to form trapezoidal cutouts 90a, 90b at the
CA 02193933 2004-11-26
25088-154
27
predetermined interval in the upper edges of the ridges
89a, 89b and bend the opposite side edges of the blank
in the direction of projection of the ridges 89a, 89b
to form circular-arc portions 85a, 85b. The resulting
rolled aluminum sheet having the cutouts 90a, 90b in
the ridges 89a, 89b, i.e., component member 94, is bent
at the midportion of its width like a hairpin to obtain
a right side wall 88. The side edges are brazed as
butted against each other to join the upper and lower
circular-arc portions 85a, 85b and form a left side
wall 85. The downward ridges 89a are brazed to the
upward ridges 89b to form reinforcing walls 89, with
the cutouts 90a, 90b combined to form hexagonal
communication holes 90 at the midportions of the walls
89 for holding parallel refrigerant passages 74 in
communication with one another. In this way. a flat
heat exchange tube A2 is obtained.
Embodiment 4
This embodiment is shown in FIGS. 16 and 21.
The process of the embodiment produces a flat heat
exchange tube A3, which as shown in FIG. 16, has the
same construction as the tube of Embodiment 1 except
that reinforcing walls 100 each having trapezoidal
communication holes 101 in the upper end and
reinforcing walls 100 having like holes 101 in the
CA 02193933 2004-11-26
25088-154
28
lower end are arranged alternately.
The tube A3 is formed by a single component member
102. As shown in FIG. 21, the component member 102
comprises a central flat portion 92 at the midportion
of its width for providing a right side wall 88~ a
right flat portion 91 providing an upper wall 86,
ridges 100a providing reinforcing walls 100 and a
circular-arc portion 85a providing the upper half of a
left side wall 85 which are positioned at the right
side of the central flat portion 92; and a left flat
portion 93 providing a lower wall 87, ridges 100b
providing the other reinforcing walls 100 and a
circular-arc portion 85b providing the lower half of
the left side wall 85 which are positioned at the left
side of the central flat portion 92. The ridges 100a,
100b have respective trapezoidal cutouts l0la, lOlb
providing communication holes 90. The ridges 100a on
the right flat portion 91 are smaller by one in number
than the ridges 100b on the left flat portion 93, and
are displaced toward the right side edge of the
component member 102 relative to the latter ridges by
1/2 of the ridge pitch.
The tube A3 is produced in the same manner as the
tube of Embodiment 3 with the exception of the
following features of the central work roll. While the
2193933
29
central work roll is formed with parallel annular
grooves at opposite sides of the midportion of its
length, the grooves at the right side are displaced
from the grooves at the left side by 1/2 of the groove
pitch toward the right roll end, and are smaller by one
in number than the left grooves. The annular grooves
have twice the depth of the annular grooves of
Embodiment 3.
Using the central work roll, a rolled aluminum
sheet, i.e. component member 102, is obtained which has
cutouts lOla, lOlb in the respective ridges 100a, 100b.
The right side wall 88 is formed by bending the member
102 at the widthwise midportion thereof like a hairpin,
the left side wall 85 is formed by butt-brazing the
opposite side edges and thereby joining the circular-
arc portions 85a, 85b, the reinforcing walls 100 are
formed by brazing the ridges 100a of the upper wall 86
to the flat portion of the lower wall 87 and the ridges
100b of the lower wall 87 to the flat portion of the
upper wall 86 alternately, and the openings of the
cutouts lOla, 101b in the ridges 100a, 100b are closed
with the flat portion to form trapezoidal communication
holes 101 in the parallel reinforcing walls 100 at
upper and lower positions alternately for holding
parallel refrigerant passages 74 in communication with
CA 02193933 2004-11-26
25088-154
one another.
Embodiment 5
This embodiment is shown in FIGS. 17 and 22.
The process of the embodiment produces a flat heat
5 exchange tube A4, which has the same construction as
the tube of Embodiment 1 except that trapezoidal
communication holes 106 are formed in the lower ends of
reinforcing walls 105 as shown in FIG. 17.
The tube A4 is formed by a single component member
10 107. As seen in FIG 22, the component member 107
comprises a central flat portion 92 at the midportion
of its width for providing a right side wall 88; a
right flat portion 91 providing an upper wall 86,
ridges 105a providing reinforcing walls 105 and a
15 circular-arc portion 85a providing the upper half of a
left side wall 85 which are positioned at the right
side of the central flat portion 92: and a left flat
portion 93 providing a lower wall 87 and a circular-arc
portion 85b providing the lower half of the left side
20 wall 85 which are positioned at the left side of the
central flat portion 92. The ridges 105a have
trapezoidal cutouts 106a providing the communication
holes 106.
The flat heat exchange tube A4 is produced in the
25 same manner as the tube of Embodiment 3 with the
2193933
31
exception of the following feature of the central work
roll. The central work roll has parallel annular
grooves only at the right side of the lengthwise
midportion thereof, and the annular grooves have twice
the depth of the annular grooves of Embodiment 3.
The tube A4 is prepared from a rolled aluminum
plate, i.e. component member 107, obtained using the
central work roll and having cutouts 106a in ridges
105a, by bending the member 107 at the widthwise
midportion like a hairpin to form a right side wall 88
and butt-brazing the opposite side edges, joining upper
and lower circular-arc portions 85a, 85b to form a left
side wall 85, brazing the ridges 105a of an upper wall
86 to the flat portion of a lower wall 87 to form
reinforcing walls 105, and closing the openings of the
trapezoidal cutouts 106a in the ridges 105a with the
flat portion to form trapezoidal communication holes
106 in the lower ends of the walls 105 for holding
parallel refrigerant passages 74 in communication with
one another.
Embodiment 6
This embodiment is shown in FIGS: 23 and 24.
The process of the embodiment produces a flat heat
exchange tube A5 which has the same construction as the
tube of Embodiment 1 except that the tube A5 has a
219333
32
right side wall 110 with a circular-arc outer surface
and a vertical inner surface as shown in FIG. 23.
As shown in FIG. 24, the flat heat exchange tube
A5 is formed by upper and lower two component members
112, 114. More specifically, the upper member 112
comprises a flat portion 111 providing an upper wall
86, downward ridges 89a providing the upper halves of
reinforcing walls 89 and portions 85a, 110a having a
circular outer face and providing the upper halves of
opposite side walls 85, 110. The lower member 114
comprises a flat portion 93 providing a lower wall 87,
upward ridges 89a providing the lower halves of the
walls 89 and portions 85b, 110b having a circular-arc
outer surface and providing the lower halves of the
side walls 85, 110: The ridges 89a, 89b have
respective trapezoidal cutouts 90a, 90b providing the
upper halves and lower halves of communication holes
90.
The flat heat exchange tube A5 is produced by the
following process.
First, upper and lower components members 112, 114
are prepared using two apparatus which are the same as
the one used for practicing the process of Embodiment 1
and shown in FIGS. 4 and 5.
In this case, the central work roll 35 and the
I
CA 02193933 2004-11-26
25088-154
33
planetary work roll 36 of the finishing rolling mill 33
of one of the apparatus have such a cross section that
with reference to FIG. 20, the right-end groove 95 of
the central roll 35 and the flange 98a of the planetary
roll 36 are respectively the same as the left-end
groove 96 of the former and the flange 98b of the
latter in symmetry a.t.opposite sides, with only half
portions of parallel annular grooves formed between the
opposite end grooves. The central work roll 35 and the
planetary work roll 36 of the finishing rolling mill 33
of the other apparatus have such a cross section that
with reference to the same drawing, the left-end groove
96 of the central roll 35 and the flange 98b of the
planetary roll 36 are respectively the same as the
right-end groove 95 of the former and the flange 98a of
the latter in symmetry at opposite sides, with only
half portions of parallel annular grooves formed
between the opposite end grooves.
Aluminum sheet blanks each comprising a brazing
sheet having a brazing material layer over opposite
surfaces are rolled by the two rolling mills to thin
the blanks to a specified thickness and form flat
portions 111, 113, cause the annular grooves to form
ridges 89a, 89b projecting from the flat portions 111,
113 integrally therewith, cause the projections within
2193933
34
the grooves to form trapezoidal cutouts 90a, 90b at a
predetermined interval in the upper edges of the ridges
89a, 89b and bend opposite side edges in the direction
of projection of the ridges 89a, 89b to form portions
85a, 110a, 85b, 110b each having a circular-arc outer
face. The two roiled aluminum sheets obtained, i.e.
upper and lower component members 112, 114, are butt-
brazed as opposed to each other at the edges at each
side, the upper and lower portions 85a, 110a; 85b, 110b
having a circular-arc outer face are joined to obtain
opposite side walls, with the flat portions 111, 113 of
the upper and lower component members 112, 114 serving
as upper and lower walls 86, 87, and the downward
ridges 89a are brazed to the upward ridges 89b to form
reinforcing walls 89, with cutout portions 90a, 90b of
the ridges 89a, 89b combined to form hexagonal
communication holes 90 at the midportion of height of
the reinforcing walls 89 for causing parallel
refrigerant passages 74 to communicate with one another
therethrough. In this way, a flat heat exchange tube
A5 is prepared.
The upper walls of the flat heat exchange tubes of
Embodiments 1 and 2, the upper and lower walls of the
tubes of Embodiments 3 to 6 may be formed with heat
transfer area increasing low projections as in the case
2193933
of the lower wall of Embodiment 1.
According to all the foregoing embodiments, the
central work roll of the finishing rolling mill has
various annular grooves, whereas such annular grooves
5 may alternatively be formed in the planetary work
rolls.
With all the foregoing embodiments, cutouts are
formed in the ridge simultaneously when the aluminum
sheet blank is passed through the finishing rolling
10 mill, while the cutouts may be formed separately after
the blank has been passed through the mill. In this
case, the projections need not be formed on the bottom
face defining the annular groove of the central work
roll.
