Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates generally to a machine
for forming a serpentine heat exchanger having a preselected
length from a continuous supply of tubing. The machine
includes a feed mechanism that advances tubing in preselected
increments to a forming and bending heat which deforms the
section of tubing to be bent prior to successively bending
each of the increments in alternative directions.
The tubing is deformed in the bend area into an
elliptical or oval configuration having its major axis paralle
to the plane of the tube. During the bending operation
the wall in the area of the outer curve moves radially inwardly
to decrease the dimension of the major axis due to its
inability to elongate sufficiently, while the dimension
of the minor axis increases so that a tube passageway having
a predetermined design area is maintained. After a pre~
determined number of successive bending operations have
been completed the serpentine heat exchanger formed by the
present invention is severed or cut off from the continuous
tube at a precise design point to eliminate any need for
successive cutting operations and in effect the elimination
of scrap and waste is realized.
In the manufacture of serpentine heat exchangers
it has been common practice to provide a length of tubing
which was bent either between a wheel or shoe with the inside
of the tube occupied by a mandrel to maintain the round-
ness of the tube passageway during the bending operation.
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In actual practice it is extremely difficult to
provide the exact length of tubing for a particular ser-
pentine heat exchanger to be formed, and, in fact, the
length of tubing provided is usually longer than the design
length of the completed heat exchanger. This practice is
necessary to allow for variations due to stretch and size
of bend radiuses. Accordingly the heat exchanger as formed
must then be trimmed to the exact length needed for a par-
ticular application which, results in a certain amount of
waste or scrap.
The practice of employing internal mandrels has
many disadvantages, for example, the length of the tubing
in the heat exchanger is limited by the length of the man-
drel. In practice when using tubes having a .375 inch
diameter, the maximum practical length of the mandrel has
been found to be about 25 feet. As a result, in many in-
stances, several heat exchangers so formed must be joined
to provide some of the volume requirement when they are
used in refrigeration systems. Other disadvantages arise
when the mandrel scores the inner wall surface of the tubing
which may lead to undesirable refrigerant flow character-
istics. The use of internal mandrels also in some instances
allows contaminants to be present in the final heat exchanger.
These contaminants, when present and if not removed, may lead
to blockage in the refrigerant system, especially in re-
stricted areas such as capillary tubes and could result in
compressor failure.
SUMMARY OF THE INVENTION
; The present invention provides a machine for forming
a serpentine heat exchanger having a predetermined length from
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a continuous tubing, wherein a forming and bending head is
adapted to successively bend increments of the continuous
tube in alternate directions about a central axis.
The continuous tube is received in a support structure
from a supply of continuous tubing with its longitudinal
axis in a plane substantially perpendicular to the central
axis of the forming and bending head. Prior to advancing
the increments of tubing to be bent about the central axis,
the tube is shifted laterally so that the successive increments
to be bent are arranged on alternate sides of the central
axis diametric to the direction of the bending.
The tube is fed longitudinally in predetermined
increments past the head so that a selected portion of the
increment, generally the trailing portion to be bent, is
arranged between shaping members or forming portions associated
with the forming and bending head. The head is driven longitudin- -
ally along its central axis so that the shaping member deforms
the selected portion of the increment into an elliptical or
oval cross section having its major axis lying parallel to
the plane of the tubing. A wall portion of a subsequent
increment diametric to the direction of the bending operation
is held against lateral movement to insure that a parallel
relationship between the increments is attained by the
bending operation.
With the selected portion arranged between the
; shaping members, the head is rotated or oscillated in one
direction 180 about the central axis so as to bend the
selected portion about the central axis and in effect bring
the increment into substantially parallel relationship with
the subsequent continuous tube. When the serpentine heat
exchanger reaches a predetermined configuration in length
it is then severed from the continuous tubing, and the
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machine then recycles and another serpentine heat exchanger
is started from the continuously fed tubing.
In forming the serpentine heat exchanger of the
present invention from a continuous tubing, the use of an
internally applied mandrel is not possible. Accordingly by
the present invention a serpentine heat exchanger is in fact
fabricated without employing an internally applied mandrel
by deforming the tubing in the area to be bent to allow
bending of the tube 1~0 without collapsing the tube ~n
the bend area.
It is an object of the present invention to fab-
ricate a serpentine heat exchanger from a continuously
supplied tube by bending preselected increments of tubing
about a central axis.
Another object of the invention is to deform the
tube in the bend area into a cross sectional configuration
that will cause the resulting stretching of the wall in the
area of the outer curve to reshape the tube walls.
BRIEF DESCRIPTION OF T~E DRAWINGS :
Figure 1 is a`plan view showing a typical serpen-
tine spine fin heat exchanger formed by the apparatus of
the present invention;
Figure 2 is a schematic view of another heat ex-
changer formed by the apparatus of the present invention;
Figure 3 is a schematic view of still another heat
exchanger formed by the apparatus of the present invention;
Figure 4 is an elevational view of the apparatus
of the present invention;
Figure S is an enlarged elevational view of the
heat exchanger forming machine of the present invention;
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Figure 6 is similar to Figure S with parts in a
second position;
Figure 7 is an enlarged sectional view taken along
lines 7-7 of Figure 6 showing details of the advancing
mechanism;
Figure 8 is a plane view taken along lines 8-8 of
Figure 7 showing further details of the advancing mechanism;
Figure 9 is an elevational view partly in section
showing the indexing portion of the advancing mechanism;
Figure 10 is similar to Figure 9 with parts in a
second position;
Figure 11 is a partial elevational view of the ad-
vancing mechanism of Figure 7 with the holding member in a
second position;
Figure 12 is an elevational view taken along lines
12-12 of Figure 6 showing the aligning and shifting mech-
anism of the present invention;
Figure 13 is a partial elevational view of the head
in the active position;
Figure 14 is a schematic view of the tube in its
deformed state;
Figure 15 is a schematic similar to Figure 14 with
; the parts moved to provide clearance;
Figure 16 is a sectional view taken along lines
16-16 of Figure 6 showing the cutoff mechanism of the
present invention; and
: Figure 17, 18, and 19 are schematic views showing
different stages in forming the heat exchanger of the
present invention.
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DETAILED DESCRIPTION OF THE INVENTION
Referring to Figure 1, there i9 illustrated a
typical heat exchanger 10 fabricated by the apparatus of
this invention wherein increments of spine fin tubing are
bent about a central axis A of Figure 4. While the heat
exchanger 10 illustrated includes five return bends joined
by tubes of equal lengths it should be understood that hy
the machine of ~he present invention a heat exchanger h~ving
any number of configurations can be fabricated and Figures 2
and 3 illustrate some of the typical vàriations that may be
formed.
With reference to Figure 4, the preferred apparatus
for carrying out this invention may be conveniently divided
into components 12, 14, 16 and 18 for ease of description.
Component 12 represents a machine 12 for producinq
continuous spine fin tubing 13 as shown and described in
U.S. Patent 3,688,375-Venables III, assigned to General
Electric Company, assignee of the present invention. Com-
ponent 14 represents a tube feed compensating means which,
as will be expl~ined hereinafter, regulates the flow of tubing
between the continuous feed of the spine fin forming machine
12 to the increment feed requirements of the heat exchanger
10. Component 16 is utilized to straighten the tube 13 as
it enters component 18 which, as will be described in detail,
is the serpentine heat exchanger forming machine 18 of the
present invention.
The spine fin tubing ma~ be made continually in
machine 12 from a rotatably supported stock roll 15 that may
contain 2,000 and sometimes as much as 10,000 linear feet
of tubing.
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Within the present embodiment the heat exchanger
10 is made in conjunction with the spine fin tubing 13 as it
is received continuously from the spine fin wrapping machine
12. It should be noted that the completed spine fin tubing
13 may be stored on rolls and the heat exchanger 10 may then
be fabricated from material supplied from the rolls.
When, for continuous automatic operation, the spine
fin material is received directly from the forming machine 12,
means must be provided to compensate between the continuous
feed rate of the spine fin forming machine 12 and the inter-
mittent feed requirement of forming machine 18. ~o this end
the feed compensating means 14 includes a holding frame 20
wherein a predetermined length of tubing 13 received from
machine 12 may be stored, Switch or control means are pro-
vided to regulate between a predetermined minimum and maximumlensth of tubing 13 stoxed in frame 20. To this end a con-
trol 21 is emplo~ed to interrupt the operation of the ~Irapping
machine 12 when the maximum length is 5ensed and a control 22
to terminate operation of the forming machine 18 when the
tubing 13 stored in frame 20 reaches a predetermined minimum
length. ~r,
The component 16 as mentioned hereinbefore is the
tube straightening portion of the apparatus for carrying
out the present invention and includes a plurality of spaced
rollers 24 arranged on either side of the longitudinal axis
of the tube 13 so that axis of the tube 13 as it leaves the
final rollers is arranged in a substantially straight line
as it enters the forming machine 18. :
Referring now to Figures 4-11 of the dra~ings, an
advanciny. mechanism 26 arranged in a support structure or :
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frame 28 of the machine 18 is effective in advancing the
tube 13 in preselected increments relative to the central
axis A. The tube 13 is received in a tubular guide member
25 supported on brackets 23 forming a part of the advancing
mechanism 26, The tube guide member 25 is positioned to
locate the longitudinal axis of the tube 13 so that it lays
in a plane C perpendicular to the central axis A. The ad-
vancing mechanism 26 includes guide means or slide frame 30
and a tube ad~ancing portion 31 which is arranged for longi-
tudinal movement on frame 30 relative to the central axisA. The frame 30 includes parallel spaced guide rails 32
(Figures 7 and 8) which includes recesses or tracks 34 for
slidably receiving a support plate 35 of tube advancing
portion 31. Arranged on the support plate 35 are a pair
of tube holding or gripping members 36 which are movable
laterally xelative to each other on a bracket 38 secured
to plate 35, The lower portion of members 36 includes
holding portions 39 which are positioned so as to be arranged
diametrically of the longitudinal axis of the tube ~3.
Secured to the portions 39 are gripping fingers or plates
40 which project radially toward the axis of tube 13 and
. are adapted to engage tube 13 as shown in Pigure 7. The
fingers 40 are spaced so as to extend between the spi.ne fin
and engage the tube wall without unduly deforming the fins
which could result in loss of heat exchange efficiency. A
pair of actuators 41 in the form of actuators or air cylin-
ders arranged on bracket 38 are operable at a selected time
to move members 36 relative to each other to cause fingers 40
to engage tube 13 and alternatively to disengage from tube 13. -
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Mounted on the upper surface of support plate 35
(Figures 9 and 10) are a series of dampers 42 which are
arranged to engage stop members 43 which are selectively
mounted on the stationary frame 30 relative to the central
axis. Referring to Figures 9 and 10, it will be seen that
the stop members 43 are arranged for vertical travel on a
support structure 44 which is adjustably mounted on the
frame 30. In operation a selected stop 43 is moved by an
operating member 46 into the path of a cooperating damper
42 to control and index the tube advancing portion 31 in its
retracted position relative to the central axis as shown in
Figures S and 9. The cooperating dampers 42 and stops 43
are arranged axially relative to longitudinal travel of the
tube 13 as will be explained hereinafter to provide pre-
selected increments of travel of the tube advancing portion
31. To prevent movement of the stop 43 relative to the
frame 30 in impact with the damper 42, a gear rack segment
48 movable with stop 43 engages a cooperating rack 50
secured to the stationary frame 30,
As shown in Figures 9 and 10, the retracted posi-
tion of the advancing portion 31 relative to the central
axis, and the length of the tube increment B advances, is
determined by the position of the stop members 43 on the
frame 30. It should be noted that a selectively located
stop 43 must be provided for each desired increment of tube
movement to engage a cooperating damper 42. For example,
the heat exchanger configuration shown in Figures 2 and 3
require that the length of tubing between return bends be -
different and, accordingly, the advancing portion 31 must
ba positioned a selected retracted position for each length
of increment required.
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As the advancing mechanism is retracting to its ,
preselected position relative to the central axis A, the
actuators 41 are in their retracted positions as shown in
Figure 11 and accordingly maintain the fingers 40 out of
engagement with the tube 13. At the preselected time in
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the forming operation while the advancing portion 31 is in
its selected retracted position against an appropriate
: stop 43, the actuators 41 are energized and as shown in
Figure 7, the fingers 40 move to engage and grip the tube -'
13 securely therebetween.
Means are provided to move the advancing portion
31 longitudinally relative to the frame 30. To this end
with the tube 13 securely held by the fingers 40, an actu- -
ating ram or member (not shown) is energized to move and
', 15 advance the portion 31,on the frame 30 from the retracted
- position against a preselected stop 43 as shown in Figures
, 5 and 9, to the advanced position as shown in Figures 6 and
10 against a fixed stop 51 secured to frame 30. In this
. position the selected increment of tubing B has been movéd
' 20 to an advanced position relative to the central axis A.
~ The advanced increment of tubing is supported on a suitable
.' table or support surface 45.
'` As mentioned hereinbefore, to form the serpentine :
' heat exchanger 10 in accordance with the present invention,
the spine fin tubing 13 is bent in alternate directions
about the central axis A. Accordingly means are provided
for positioning the advanced increment B of tubing on
l alternate sides of the central axis A.
-~'' To this end a shifting mechanism 52 as shown in 5
~ 30 Figures 5, 6, and 12 is arranged on the support 28 for
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lateral movement relative to the longitudinal axis of the
tube 13. The mechanism 52 is mounted on stationary plate
54 which has rails 56 supported therefrom. Slidably
mounted on the rails 56 is a platform 58 which is connected
to an actuator 60. The slide frame 30 is pivotally
connected at 57 to the rParward end of platform 58 so
that lateral movement of the platform 58 on rails 56 by
the actuator 60 causes the advancing mechanism 26 to shift
laterally. This lateral movement of the advancing mech-
anism 26 carries with it the guide member 25 which con-
centrically supports the tube 13 and, accordingly, the
tube 13 is shifted to a selected side of the central axis
A to be in position for the following alternate bending
operation.
Associated with the central axis A (Figures 4, 5,
6, and 13) is a forming and bending head 65 having forming portions
or shaping members which comprise cooperating upper and lower
portions 62, 63 respectively. The portions 62, 63 are
mounted for synchronous rotational oscillations in alternate
directions about a central A and for reciprocal axial movement
relative to each other. To this end the portions 62, 63 are
; mounted for reciprocal movement on guides 62' and 63'
respectively. The guides are adapted to be moved axially
relative to each other by a cooperating mechanism 68. A drive
means 71 associated with guide 63' of portion 63 is effective
when the portions 62 and 63 are engaged to rotate the he~d
65 in alternate directions about the central axis A.
Referring now to Figure 13 it will be seen that the portions ~ -
62, 63 including the forming or shaping surfaces 66 thereon
are diametrically arranged about plane~ and aligned along
central axis A. At the propex time in the sequence
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of operation the portions 62, 63 are moved axially toward
each other by mechanism 68 so that the surfaces come to-
gether and meet substantially in the plane C to clamp the
tube 13 between the surfaces 66.
With the tube 13 held between the surfaces 66,
the head 65 is rotated approximately 180 about a cam 67
centrally arranged on axis A in one direction until the -
- advanced increment B of tube 13 is arranged substantially
parallel to the following or subsequent portion 70 of
tube 13.
In bending a tube having a diameter of .375 inches
and a wall thickness of between .035 and .020 lnches wherein
the radius of the tube axis in the bend is approximately
.565, means must be provided to prevent the movement or
collapse of the tube wall in a radial direction to the bend
due to the inability of the wall in the area of the outer
curve to stretch an amount sufficient to maintain its radial
position relative to the wall in the area of the inner curve.
This collapsing of the tube walls is of course not acceptable
in that it effects the design flow characteristics of re- -
frigerant and means must be provided to prevent the collap-
sing of the tube 13 in the bend area 69.
Accordingly by the present invention, the portion ~-
69 of the increment B that, as shown in Figure 1, repre-
sents the return bend area in the completed heat e~changer
10 is deformed prior to bending operation. The portion 69
of spine fin tube 13 is deformed as shown in Figures 13 and
14 by the portions 62, 63 as they are brought together and
accordingly only the spine fins in the return bend area are
~0 unduly deformed. To this end the surfaces 66 when brought
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together with sufficient pressure to deform the portion 69
are so dimentioned that the tube 13 will assume a cross
sectional configuration resembling an oval or ellipse having
a major axis D.
The major axis D of the deformed cross sectional
configuration is parallel to the plane C. As can easily be
understood with the deformed portion 69 positioned between the
surfaces 66, the subsequent rotational movement of head 65
will cause the wall in the area of the outer curve to try
to stretch to form the outer circumference of the completed
bend. As mentioned hereinbefore during the bending operation
the outer wall in its inability to stretch sufficiently
to maintain its radial position relative with the inner
wall, will move radially inwardly while at the same
time the tube diameter along the minor axis expands so that
the tube cross sectional configuration will tend to reform
to substantially the original round configuration thereby
maintaining a clear unobstructed design passageway. After
the deforming operation the surfaces 66 are so spaced (Figure
14) that they will allow the reshaping of the tube portion 69.
In the bending operation as increment B is bent
about the central axis, the subsequent or following increment
70 of tube 13 adjacent the head 65 tends to move laterally
from the longitudinal axis of the tube in a direction
diametric to the bending operation.
Accordingly, with reference to Figures 5, 6, and
12, it will be seen that in fabricating the heat exchanger
10 in accordance with the present invention, means are pro-
vided to prevent movement of the portion 70 during the
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bending operation of increment B. A tube aligning mech-
anism 72 is mounted for lateral movement with the shifting
mechanism 52 and more particularly to the plate 58. The
aligning mechanism 72 includes a frame member 74 mounted
on guide rods 80 which are slidably arranged in support
blocks 82 secured to plate 58. Pivotally mounted on the
frame 74 are a pair of arms 76 including tube holding
blades or members 77. The arms 76 are pivoted at 79 on
frame 74 at a position above the guide member 25 and
tube 13. The arms 76 are moved alternatively by a pair
of actuators 78 so that the members 77 engage the tube 13.
Since lateral movement of tube 13 occurs in a direction
diametric to the bending operation, the actuators 78 are
energized alternatively so that the arm 76 and holding
member 77, moved, engages a portion of subsequent increment
; s of the stationary tube side wall that in fact is an ex-
tension of the wall of the outer curve. It should be noted
that members 77 are fabricated from relatively thin metal
so that a minimum number of spine fins are deformed. ~:
Referring to Figure 6, .in order to be effective
in preventing lateral movement of tube 13 in portion 70,
the member 76 should engage the tube wall portion adjacent
the head 65 and in effect, during the bending operation the
mechanism 72 is allowed to move forward on guide rcds ~0
from the position shown in Figure 5 ~o that of Figure 6.
After the bending operation and prior to the next bending
operation, the aligning mechanism 72 is positively retrzcted
relative to the forming head 65 by an actuzto~ 83. Prior
to a banding operation the mechanism 72 is in its retracted
position as shown in Figure 5 and both holding members 76
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are rotated or pivoted away from the tube 13, Immediately
prior to the bending operation the appropriate members 76
are pivoted into engagement with the tube 13 in increment 70.
After a predetermined number of alternate bending
operations the heat exchanger 10 is cut from the continuous
tube 13 so that another heat exchanger can be fabricated
from the continuous tube 13. To this end a cutoff mech-
anism 85 is provided (Figure 16) wherein a cutter 86 is
located below the plane C of tube 13 and a cooperating
cutter 87 is arranged above tube 13. Both o~ the cutters
86 and 87 are arranged for vertical movement on guides B8
formed in blocks 89. It should be noted that cutter 87,
which is mounted on plate 54, is shifted laterally by the
shifting mechanism so that upper cutter 87 moves laterally
with, and is always properly positioned, over tube 13 and
accordingly a single U-shaped cutting area 91 is provided.
The lower stationary cutter 86 is provided with two cutting
areas 92 so that the tube 13 is aligned with one of the
cutting areas in either of its shifted positions relative
' 20 to the central axis A. In operation, an actuator 93 effec-
tively drives cutter 87 vertically downwardly whi].e cutter
86 is driven upwardly by actuator 94 so that the cutting
area 91 and the cooperating cutting areas 92 are driven
through the tube 13.
Referring now to Figures 17-19, there are shown
the steps in fabricating the heat exchanger illustrated.
In progressing through the forming of the heat exchanger,
it will be assumed that to start with, the free end of a
continuous spine fin tubing is located at a point adjacent
the head 65 and more specifically at the point, a previously
fabricated heat exchanger may have been cut off.
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In operation, with the advancing portion 31
located longitudinally at a preselected location by an
appropriate stop 43, the holding portion 39 is actuated
to engage the tube and move it forward a preselected in-
crement by action of the advancinq mechanism 26. Thisforward movement of tube 13 is selected so that the trailing
end or portion 69 of increment B forming the return bend is
arranged between the shaping surface 66. The shifting mech-
anism 52 is then actuated to laterally arrange its assoc-
iated mechanism including increment B of tube 13 and morespecifically portion 69 to one side of the central a~is A.
The holding member 76 moves to engage the side wall of the
subsequent tube portion to prevent movement of the stat-
ionary tube portion in a direction diametric to the bending
direction. The advancinq mechanism retracts to a preselected
distance to engage an appropriately arranged stop. The
head members 62, 63 move axially toward each other until
the surfaces 66 engage portion 69 with sufficient pressure
to deform the tubing into the generally oval configuration
so that it has its major axis D arranged parallel with the
plane C and perpendicular to the central axis A. The head
65 then rotates in one direction to form the first return
bend of the heat exchanger. The rotation of head 65 in
each direction is substantially 180 so as to locate in-
crement B parallel to the subsequent increment 7~ of tube13 to be bent. The above described steps are repeated
until the desired number of return bends and length of heat
exchanger 10 is attained, at which time the cutoff mech-
anism 85 is actuated and the heat exchanger 10 severed from
the continuous tubing 13.
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In adapting the apparatus to be used in an auto-.
matic production operation, the table portion 45 that
supports the severed heat exchanger 10 is pivoted at 96
and rotated downwardly by an actuator 97 so that the com-
pleted heat exchanger 10 may slide down onto a conveysystem 100.
It should be apparent to those skilled in the
art that the embodiment described heretofore is considered
to be the presently preferred form of this invention. In
accordance with the patent statutes, changes may be made
in the disclosed apparatus and the manner in which it is
used without actually departing from the true spirit and
scope of this invention.
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