Note: Descriptions are shown in the official language in which they were submitted.
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Description
Method And Apparatus For Flattening
Corrugated Heat Exchanger_Plates_
Technical Field
The present invention relat:es generally to
heat exchangers and more particularly to a method and
apparatus for use in the formation of thin metal plates
used in such heat exchangers.
Background Art
Primary surface recuperators have been
developed which incorporate thin alloy metal sheets
that have been Gorrugated or folded to produce passages
on both sides of each sheet. These passages serve to
direct the flow of air and hot gasses, and heat is
transferred directly through the sheets which are
suitably welded together to prevent the flow of air
into the gas passages. The corrugations in the sheet
surface also serve to support adjacent sheets in the
assembly.
Before the sheets are assembled, edge portions
of the sheets are crushed to provide flattened header
sections which will facilitate the cross flow of
fluid. These header sections at each end of the sheet
received or deliver the air or gas from or to the
appropriate passages of the assembiy.
~ A stacked plate heat exchanger of the type des-
;~ 25 cribed i5 illustrated by United States Patent No.
3,759,323 to Harry J. Dawson et al. In fabricating
heat exchangers of this type, difficulties have been
encountered in flattening the header sections. The
header sections extend transversely to the corruga-
tions, and as the corrugations in the header sections
are flattened, the corrugations expand and often
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completely or partially block the fluid passages
defined by adjacent corrugations. Attempts to al-
leviate this problem have not been satisfactory.
For example, comb-like devices have been employed
in an attempt to open the blocked passages following
the crushing of the header section corrugation~,
but since the blockages are irregularly spaced, the
regularly spaced comb devices sometimes contribute
to the blockage instead of removing it. Also the
sheets have been staggered so that the transition
blockage does not occur all at one zone and the fluid
can pass over the blocked region, but this solution
to the problem results in the use of excess heat
exchanger materialO
lS The foregoing illustrates the limitations of
the known prior art~ Thus it is apparent that it
would be advantageous to provide an alternative to
the prior art.
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~1 Disclosure of the Invention
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~ 20 In one aspect the present invention provides
i a novel method for Elattening corrugated heat ex-
changer plates to form header sections which includes
separately and progressively crushing the corruga-
tions in a transition zone between the fluid passages
and a header section before forming the remainder
of the header section.
Another aspect of the present invention is to
provide a novel apparatus for flattening corrugated
heat exchanger plates to form header sections which
includes opposed die members for progressively crush-
ing the corrugations in a transition zone~ each die
member having blades which are maintained on either
side of a corrugation to limit the ability of the
; corrugation to expand or flare outwardly during the
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crushing operation,
The foregoing and other aspects will become
apparent from the following detailed description
of the invention when considered in conjunction with
the accompanying drawings~ It is to be expressly
understood, however, that the drawings are not in-
tended as a definition of the invention but are for
the purpose of illustration only.
Brief Description of the_Drawings
Figure 1 is a plan view of a corrugated heat
exchanger plate which is to be flattened to form
header sections in accordance with the present inven-
; tion;
Figure 2 is a diagrammatic illustration of the
die assembly of the present invention for receiving
a moving heat exchanger plate;
Figure 3 is a cross sectional view of the die
set used for the die assembly of Figure 2;
Figure 4 is a cross sectional view of one die
slot and one die blade of the die set of Figure 3
taken along lines 4-4 of Figure 3;
Figure 5 is a detailed illustration of the detent
switches used for the die assembly of Figure 2; and
~ igure 6 is a circuit diagram of the control
circuit for the die assembly of Figure 2.
Best Mode For Carry_nq Out The_In e tion
Referring now to the drawings, Figure 1 discloses
a corrugated heat exchanger plate indicated generally
at 10 formed from a thin metal or metal alloy sheet
which has been corrugated to provide raised ridges
; having crowns or fins 12 which define intermediate
: passages 14. These crowns and passages are formed
on both sides of the sheet 10, and when the sheet
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is assembled with similarly formed sheets~ will
define fluid passages on opposite sides of the sheet.
The broken lines 16 and 18 in Figure 1 designate
header zones 20 and 22 which must be formed on either
S side of a central corrugated section by flattening
the corrugations in the header zones. It is this
flattenin~ process which, in the past, has resulted
in blockage of the passages 14 in the vicinity of
the lines 16 and 18 due to expansion or flaring of
the crowns 12 as they are crushed.
In accordance with the method of the present
invention, the header zones 20 and 22 may be flattened
without resulting in substantial blcckage of the
passages 14. This is accomplished by progressively
~` 15 crushing each individual crown 12 within transition
zones 24 and 2~ bordered by the lines 16 and 18 and
broken lines 28 and 30 spaced therefrom. Each crown
within a transition zone is subjected individually
` to a plurality oE successive crushing steps during
which the crown is progressively flattened. During
each crushing step~ die set support blades are in-
serted into the passages 14 on either side of the
crown to act as spacers to prevent the crown from
expanding outwardly to block the passages. Once
the transition zones 24 and 26 are completely flattened,
the remainder of the header zones outboard of the
transition zones may be easily flattened in a con-
ven~ional manner to form transversely extending
headers on either side of a central corrugated sec-
tio~.
The preliminary progressive flattening of thecorrugations in the transition zones 24 and 26 may
be accomplished by feeding the corrugated heat ex-
changer plate 10 between opposed die members of a
die set mechanism which closes once each time the
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plate moves for a distance equal to the distance
between two adjacent crowns 12 . As the crowns move
beneath the die members, they are progressively re-
ceived in slots of ever decreasing depth as the die
members close. At least one passage 14 between the
first crown to be crushed and the next adjacent crown
to be crushed receives a die support blade which
extends into the passage for substantially the total
depth thereof to act as a locator blade for following
die set blades. This locator blade also stabilizes
and reinforces the heat exchanger plate lO during
the flattening operation.
A novel die assembly 32 constructed in accor--
dance with the present invention is illustrated di.a-
grammatically in Figure 2. This die assembly includesan upper die 34 and a lower die 36 having opposed
`~ die surfaces which are engaged and disengaged by
the operation of upper and lower hydraulic cylinders
42 and 44 respectively. the upper and lower dies
~ 34 and 36 are connected to hydraulic pistons in
cylinders 42 and 44 by rod means 38 and 40, although
other suitable known driving units may be employed
to engage and disengage the upper and lower dies.
The operation of the hydraulic cylinders 42
and 44 is controlled by a die control circuit 46
which controls a valve in each cylinder to cause
the rods 38 and 40 to extend or retract. When the
rods extend to bring the upper and lower dies 34
and 36 together, the crowns 12 on the heat exchanger
; 30 plate lO are crushed.
The heat exchanger plate lO is fed between the
upper and lower dies 34 and 36 by a suitable drive
means such as opposed driven rollers 48 and 50.
Ideally, essentially a continuous feeding motion
is imparted to the heat exchanger plate lO, and
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consequently, the operation of the upper and lower
dies must be accurately timed. This timing sequence
is accomplished in response to sensing switches 52
54 and 56A and 56B.
To comprehend the manner in which the die as-
sembly 32 operates, it is first necessary to consider
the structure oE the upper and lower dies 34 and
36 as illustrated in Figures 3 and 4 The face of
the upper die 34 is form d to provide a plurality
of downwardly extending sequential blades 58, 60,
; 62, 64 and 66 which are spaced by intervening slots
68, 70, 72, 74 and 76. Similarly, the ~ace of the
lower die 36 is formed to provide a plurality of
upwardly extending sequential blades 78, 80, 82,
84, 86 and 88 which are spaced by intervening slots
90, 92, 94, 96 and 98. When the upper and lower
dies are engaged, the blades 80~88 enter the slots
;~ 68-76 respectively while the blades 58-66 enter the
~, slots 90-98 respectively. It will be noted that
some clearance is left between a slot and the blade
receîved thereby to accomodate the heat exchanger
plate 10.
- The heat exchanger plate 10 is fed between the
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upper and lower dies 34 and 36 from the left in Figure
^~ 25 3. The blades 58, 78 and 80 constitute entrant blades
and are the first blades to enter into passages 14
in a heat exchanger plate as the plate moves between
the dies. The blade 58 enters a passage on the top
; side o~ the plate while the blades 78 and 8~ enter
individual passages on the bottom side of the plate.
These entrant blades and the slots 68 and 90 which
receive them are full size and receive and support
the heat exchanger plate without crushing the crowns
12. If desirable, a second full sized slot and blade
, 35 combination 60 and 92 may be provided so that the
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top and bottom passages 14 are supported by two
blades on ei-ther side of the heat exchanger plate
lO at -the entrant end of the die set.
The slots 70, 72, 74 and 76 in the top die 34
and the slots 94, 96 and 98 in the bottom die 36
decrease progressively in depth so that the slots
76 and 98 at the exit end of the die set are very
shallow. Thus the crowns 12 o the heat exchanger
; plate are progressively crushed as they move into
; lO slots of decreasing depth. To aid in this crushing
operation, a projection 100 extends from the root
of each slot while the opposing blade has a scalloped
end as indicated at 102 in Figure 4.
It is important to assure that an individual
passage 14 on the top of the heat exchanger plate
lO cleanly and se~uentially receives the blades 5~,
60, 62, 64 and 66 as the plate progresses from the
entrant to the exit ends Qf the die set. Simultan-
eously, an adjacent passage on the bottom side of
the heat exchanger plate seq~entially receives the
blades 78, 80, 82, 84, 86 and 88. This is accom-
plished under the control of the detent switch 52
which causes the die control circuit 46 to trigger
the die cylinders 42 and 44 to close the upper and
lower dies 34 and 36 when the heat exchanger plate
is in a precise location.
The structure of the detent switch 52 is shown
in greater detail in Figure 5. The switch includes
- a detent ball 104 mounted on a spring arm 106 which
spring biases the ball downwardly against the crowns
12 on the heat exchanger plate lO. The ball consists
of two electrically conductive halves 108 and llO
which are electrically separated by a central in-
sulating strip 112. Electrical conductors 114 and
116 are each connected to one of the conductive
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halves, so that when the ball is nested in a passage 14
as shown in Figure 5, an electrical circuit is
: completed between the conductors by the conductive
halves 108 and 110 and the heat exchanger plate. When
the ball is not in contact with the crowns 12 on both
sides of a passage 14, no electrical circuit is
completed between the conductors 114 and 116.
The die control circuit 46 is identical in
structure and operation, for flattening both zones 24
and 26 and consequently will be described with
reference to the structure of die control circuit 46
shown in Figure 6. This circuit includes input
terminals 118 and 120 which supply power to control the
operation of cylinder 42 ~Figure 2)l and input
: 15 terminals 122 and 124 which supply power to a holding
` circuit. These input terminals may be connected to the
`~ same or separate power supplies, such as a battery
power supply 140
When an electrical circuit is completed
between the conductors 114 and 116 by the detent switch
~; 52l power may be provided from the terminal 118 across
the detent switch to energize the coil 126 of a holding
relay and close relay contact 128 to keep the holding
relay actuated in the "hold" position. Power from the
holding relay will flow through solenoids 130A and 130B
~- which control a valve or other control member for the
: cylinders 42 and 44, and the die piston rods 38 and 40
will be extendedO From the solenoids 130A and 130B,
power then passes across closed contact 134 and back to
terminal 120.
The contact 134 is part of a holding relay
~:~ including a holding relay coil 136 which is kept
~; energized from terminal 122 acrcss normally closed
switches 56A and 56B after the contacts 138 have been
initially closed by a brief closure of switch 54 to
. energize the coil 136. Switches 56A and 56B
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open at the end of each die stroke.
Industrial A~?~licability
The heat exchanger plate 10 is moved between
the upper and lower dies 34 and 36 by the driving
wheels 48 and 50. The switches 56A and 56B are
normally closed and the switch 54 is open. There-
; fore, the holding relay coil 136 is normally energized
with the contacts 134 and 138 closed. As the heat
exchanger plate is located in the correct position
for the crushing operation, the detent switch 52
momentarily closes to energize holding relay coil
126 and close contacts 128. Current now flows from
terminal 118 across contacts 128 and through coil
; 12~, control solenoids 130A, 130B and contacts 134
' 15 back to terminal 120. The energization of solenoids
; 130A and 130B causes cylinders 42 and 44 to expancl
die piston rods 38 and 40 driving the dies 34 and
36 together. As the rods 38 and 40 reach the outer
extent of their travel, switches 56A and 56B are
momentarily opened to deenergize holding relay coil
136. This opens contacts 134 and 138 causing the
deenergization of control solenoids 130A, 130B and
holding relay coil 126. Upon deenergization of the
control solenoids, the rods 38 and 40 are retracted
to disengage the upper and lower dies 34 and 36 and
reclose the switches 56A and 56B. During movement
of the sheet to the next passage a switch 54 is
normally closed. The switch 54 is similar to switch
52 but is positioned to close during vement of
the sheet and prior to closure of switch 52 to affect
the next die stroke. Switch 54 is positioned appro-
ximately 1/2 passage pitch different from switch
52 so that movement of the sheet alternately engages
switches 52 and 54. This assures t.hat switch 54
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will close prior to the point where the passage in
position for switch 52 to close and actuate the die
stroke.
The detent switch 52 is located closely adjacent
the blades 58 and 80 at the entrant end of the die
set and is spaced relative to these blades so that
these entrant blades serve as lccators for the re-
maining blades in the die set. Each time a detent
switch bridges two ad~acent crowns 12, the die set
comes together and the blades formed in the faces
of the opposed dies enter the passages 1~ which are
aligned therewith. The slots 70-76 and 94-ga pro
gressively crush the crowns 12 received thereby while
the intervening blades prevent the crushed crowns
from expanding to block the passages 14~ Each crown
is subjected to a plurality of separate successive
crushing operations unkil it reaches either the slot
76 or the slot 98. These finaI exit slots are so
shallow that full crushing of the transition zones
24 and 26 is completed thereby. After these tran~
sition ~ones are completely crushed, the remainder
of the header zones 20 and 22 is crushed in the
conventional manner.
It is obvious that the blades in the Ea~es of
2S the upper and lower dies 34 and 36 will be formed
to conform ~o the configuration of the passages 14
in the heat exchanger plate 10~ Therefore, when
the passages are wavy in configuration as shown in
Figu~e 1, to enhance heat transfer, the blades will
be similarly configured to conform therewith. Also,
if the passages in one side o~ the plate vary in
width from the passages on the opposite side, the
width of the blades will also vary accordin~ly.
Thus, as will be noted in Figure 3, the blades in
the face of the lower die 36 are wider than those
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in the face of the upper die 34.
The foregoing has described a method and ap-
paratus for use in the formation of thin metal plates
used in heat exchangers.
It is anticipated that aspects of the present
invention, other than those specifically defined
in the appended claims, can be obtained from the
foregoing description and the drawings.
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