Method and assembly for manufacturing a convoluted heat exchanger core

A method of manufacturing a convoluted heat exchanger core from a continuous sheet of thermally conductive metallic material includes providing a pusher bar assembly having a table, a pusher bar plate mounted transversely across the table and a stripper bar plate mounted transversely across the table in opposed relation to the pusher bar plate. The pusher bar plate is moveable along the length of the table between a feed position that is spaced a predetermined distance from the stripper bar plate and a fold position that is located adjacent the stripper bar plate. The sheet of material is fed lengthwise onto the table and into engagement between the pusher bar plate and the table with a portion of the sheet of material located between the pusher bar plate and the stripper plate when the pusher bar plate is in the feed position. The portion of sheet material is folded into a convolution by moving the pusher bar plate to the fold position. The stripper bar plate is raised above the convolution of the sheet of material to permit the convolution to pass by the stripper bar plate along the length of the table. The stripper bar plate is lowered and the pusher bar plate is retracted to the feed position such that the pusher bar plate is in engagement with the sheet of material against the table.

This invention relates to the manufacture of convoluted heat exchanger 
cores and, in particular, to an automated process that unwinds a 
continuous sheet of thermally conductive material, such as aluminum, from 
a roll or coil, embosses the sheet of material, folds the sheet of 
material to form convolutions, and cuts the convoluted sheet of material 
into predetermined lengths to form individual convoluted heat exchanger 
cores. 
BACKGROUND OF THE INVENTION 
Heat exchangers are widely used to dissipate heat. One application is to 
protect sensitive electronic controls that are located in harsh industrial 
settings. 
Heat exchangers having convoluted aluminum cores are preferred for 
providing closed loop cooling for enclosed electronics. In such a heat 
exchanger, heated enclosure air is drawn through one side of the 
convoluted core while cooler ambient air is pulled through the 
convolutions on the other side of the core in the opposite direction. Heat 
from the enclosure air transfers through the core to the ambient air flow 
and is discharged into the atmosphere. The cooled enclosure air then blows 
back into the enclosure. Such a heat exchanger is ideal for applications 
in which the electronic controls can operate at a temperature differential 
slightly above ambient, humidity is not a factor, and ambient air 
contaminants must be kept out of the enclosure. 
Previously, convoluted cores were made by simply manually folding a sheet 
of aluminum. Various types of devices are known in the art for forming, 
crimping, folding, perforating and otherwise processing sheet or strip 
material, such as sheet metal. But these devices are generally not 
suitable for making the convoluted aluminum cores used in closed loop heat 
exchangers. 
One device used in the automotive industry for manufacturing radiator cores 
is a rolling fin machine that utilizes a gear mesh operation to form the 
convolutions as the sheet material passes between the two gears. See, 
e.g., U.S. Pat. Nos. 1,849,944; 2,252,209 and 4,507,948. Such a device, 
however, has several limitations relating to the small size of the 
convolutions that can be formed and the flexibility necessary to quickly 
adjust the machine from making cores having convolutions of one height to 
making cores having convolutions of a different height. 
Another machine for making convoluted cores is a reciprocating press 
machine, such as a Robinson fin machine. See, e.g., U.S. Pat. Nos. 
3,760,624 and 5,722,145. The Robinson fin machine uses two opposed dies, 
each moveable toward and away from the other in a vertical forming stroke 
to form the convolutions in a sheet of material that is fed between the 
dies. As with the rolling fin machines discussed above, however, the 
Robinson fin machine generally is used to make cores having relatively 
small convolutions, typically two inches or less. In addition, if a 
different core type or pattern is desired, a different machine set up is 
required. On-line set up operations include setting stripper heights, 
setting strokes, and setting tool height relative to the strippers. All of 
this is time consuming, non-productive, and obviously undesirable, 
especially when the manufacturer specializes in serving customers with 
special needs and low volume orders. 
A type of pleat forming machine is known to make accordion bellows and lamp 
shades wherein the machine includes a laterally moveable pusher bar and a 
vertically moveable stripper bar parallel to it and normally spaced 
laterally from it above a table. Generally, the stripper bar reciprocates 
along a path extending perpendicular to the moving web of material while 
the pusher bar reciprocates along a path extending generally parallel to 
the moving web, toward and away from the reciprocating stripper bar. The 
pleats are formed by compressing respective sections of web material 
between the two bars during each reciprocation cycle of the bars. 
Specifically, when the pusher bar and stripper bar are moved together, a 
section of sheet material is disposed between the two bars and is folded 
into a pleat. After each pleat is formed the stripper bar is raised, 
permitting the just formed pleat to pass by. See, e.g., U.S. Pat. Nos. 
2,677,993; 4,201,119 and 4,650,102 incorporated herein by reference. Such 
machines, however, are used to fold paper or cardboard for forming 
accordion bellows or pleated lamp shades or to fold filter media. They 
have not previously been known to be used or to be useful for folding more 
robust materials, such as metals, including aluminum. 
In view of the above, it should be appreciated that there is still a need 
for a machine that forms a continuous sheet of thermally conductive 
material, such as aluminum, into a convoluted heat exchanger core and 
which readily makes cores having convolutions ranging in height from two 
inches or less up to and exceeding twelve inches. In addition, the machine 
should permit quick adjustments to the size of the convolutions without 
removing machinery from the production line. The present invention 
satisfies these and other needs and provides further related advantages. 
SUMMARY OF THE INVENTION 
The present invention is embodied in an assembly for forming a continuous 
sheet of thermally conductive material, such as aluminum into a smooth or 
embossed convoluted heat exchanger core. The assembly significantly 
reduces the direct labor to make a convoluted heat exchanger core by 
eliminating the requirement of manual folding. The assembly also results 
in a faster production rate and permits the formation of an embossed 
pattern in conjunction with the convolutions. The assembly is also capable 
of producing any convolution height and the squareness of the cores are 
greatly improved. 
The assembly for manufacturing a convoluted heat exchanger core from a 
continuous sheet of thermally conductive metallic material includes a 
pusher bar assembly having a pusher bar plate and a stripper bar plate, 
both mounted transversely across a table in opposed relation to each 
other. The pusher bar plate is moveable along the length of the table 
between a feed position that is spaced a predetermined distance from the 
stripper bar plate and a fold position that is located adjacent the 
stripper bar plate. The sheet of material is fed lengthwise onto the table 
and into engagement with the pusher bar plate. A portion of the sheet 
material to be folded is located between the pusher bar plate and the 
stripper bar plate. The sheet material is folded into a convolution by 
moving the pusher bar plate to the fold position. The stripper bar plate 
is then raised above the convolution to permit the convolution to pass by 
the stripper bar plate along the length of the table. The stripper bar 
plate is lowered and the pusher bar plate is retracted to the feed 
position such that the pusher bar plate is in engagement with the sheet of 
material against the table and in position to form another convolution. 
A feature of the present invention is the use of the pusher bar assembly to 
fold the sheet of thermally conductive metallic material. An advantage of 
this feature is that convolutions of greater height can readily be formed. 
In particular, convolutions of two inches up to twelve inches for core 
widths of 18 to 48 inches are readily manufactured. In addition, the 
pusher bar assembly may be controlled to form consecutive cores having 
convolutions of different heights or even to change the height of the 
convolutions for any given core. This flexibility is particularly 
desirable for a manufacturer specializing in serving customers with 
special needs and low volume orders. 
Another feature of the present invention is that the assembly may include a 
press in front of the pusher bar assembly having a die set for forming an 
embossed pattern on the sheet of material. An advantage of this feature is 
that embossed heat exchanger cores may be manufactured and the combined 
assembly of the pusher bar assembly and the press can be controlled to 
manufacture smooth or embossed cores to adjust the number of emboss 
patterns per convolution, or to manufacture cores with outside 
convolutions that are embossed or smooth. 
Another feature of the present invention is that the assembly may include a 
feed control assembly in front of the press having a pair of feed rollers 
and a motor for rotating the feed control rollers. An advantage of the 
feed control assembly is that it provides accurate measurement of the 
amount of material that is fed through the press and into the pusher bar 
assembly. This permits accurate and consistent production of identical 
heat exchanger cores. In addition, the feed control assembly can include 
guide rails for controlling wandering of the sheet of material so as to 
insure the squareness of the heat exchanger cores. In addition, the feed 
control rollers and the press can be operated in such a manner as to 
permit the sheet of material to self align as it is fed through the press. 
Other features and advantages of the present invention will become apparent 
from the following description of the preferred embodiments, taken in 
conjunction with the accompanying drawings, which illustrate, by way of 
example, the principals of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The various components of a preferred assembly for manufacturing convoluted 
heat exchanger cores are shown in FIGS. 1 and 1A. 
A roll of thermally conductive sheet material 10, preferably 0.008 inch to 
0.012 inch 1100-0 temper aluminum, or other soft aluminum material, is 
mounted on a support stand 12 and fed through a motorized unwind stand 14. 
A feed control assembly 15 includes a stand 16 that supports a pair of 
feed rollers 18. The rollers feed the sheet material into a press 20. The 
press stamps an emboss pattern into the sheet material. A pusher bar 
assembly 22 then takes the embossed sheet material and folds it to form 
convolutions. When a predetermined number of convolutions are formed, a 
core cut-off assembly 24 cuts them from the sheet material to form a heat 
exchanger core 26. A control system 28 permits adjustments in convolution 
height, the number of convolutions per core, and the number of emboss 
patterns per convolution. The control system also permits the choice of a 
smooth or embossed core, a multiple convolution height core, outside 
convolutions that are embossed or smooth, and the provision of smooth end 
flaps on the core for assembly. 
With reference to FIG. 2, the support stand 12 includes a shaft 30 for 
receiving the roll of thermally conductive sheet material 10. Preferably, 
the support stand includes a brake (not shown) to prevent the roll of 
sheet material from uncoiling too quickly. The roll is uncoiled from the 
back and fed between rollers 32 of the unwind stand 14. Preferably, one of 
the rollers is movable vertically, for example by an air cylinder 34, to 
permit the sheet material to be fed through or to permit alignment of the 
sheet material. 
The sheet material is unwound from the roll by rotation of the rollers 32 
and forms a loop 36 between the unwind stand 14 and the feed control stand 
16. A loop control 38 activates the rollers in response to an upper loop 
sensor 40 and a lower loop sensor 42 located adjacent the unwind stand. 
The loop sensors are mounted to a support stand 44 having a vertical strut 
that supports the upper loop sensor at a predetermined distance above the 
lower loop sensor. It will be appreciated that the loop of sheet material 
formed between the unwind stand 14 and the feed control stand 16 is 
controlled by the loop sensors in that the lower loop sensor 42 will send 
a signal to the loop control 38 to stop rotation of the rollers 32 and the 
upper loop sensor 40 will send a signal to the loop control to activate 
the rollers. Preferably the loop sensors are photoelectric sensors which 
can sense the edge of the aluminum sheet when it passes in front of the 
respective sensor. Other methods of monitoring the loop of sheet material 
are well known in the art, such as sonar sensors and dancer arm/switch 
mechanisms. 
The unwind stand 14 preferably includes an anti-kink shield 48 to help 
insure that the sheet material pulled through the rollers will form an 
even and smooth loop between the unwind stand and the feed control stand. 
Preferably, the anti-kink shield extends the width of the sheet material 
and may be pivotably supported at each end by struts 50 coming off the 
sides of the unwind stand. If desired, the struts can be spring loaded at 
56 away from the unwind stand (see FIG. 2A) to permit the loop 36 to begin 
forming before it contacts the anti-kink shield. 
With reference to FIGS. 3 and 4, the feed control stand 16 includes a frame 
60 having two side walls 62. A bottom roller 64 has an axle 65 that is 
rotatably supported in bearings 66 mounted in the side walls. A 
servo-drive motor 68, including an amp and gear box is preferably mounted 
to the frame, and operates a timing belt 70 which drives the axle 65 of 
the bottom roller 64 (FIG. 3A). A top roller 72 forms a nip with the 
bottom roller. The top roller has an axle 73 that is supported from a 
support shaft 74 that extends transversely between the side walls. A pair 
of air cylinders 76 also support the top roller. Each end of the support 
shaft 74 is mounted in a bearing 77 located in the side walls of the 
frame. Pivot arms 78 are connected between the shaft 74 and the axle 73 of 
the top roller. One end of each pivot arm is connected to one end of the 
shaft and the other end of each pivot arm is rotatably connected to a 
respective end of the axle of the top roller. The air cylinders are 
preferably mounted to an upper support 79 of the frame. Piston rods 80 
extending from the cylinders are connected to the respective pivot arms 78 
near the top roller to actuate movement of the top roller between an open 
position, wherein the top and bottom rollers are spaced apart and a closed 
position wherein the top and bottom rollers form a nip through which the 
sheet material 10 is fed. In the preferred embodiment, the top and bottom 
rollers are six inch diameter steel plated rollers. The control system 28 
controls the operation of a valve (not shown) connected to the air 
cylinders. The control system also operates the servo-drive motor, as will 
be discussed in detail below. 
In the preferred embodiment, a slide table 102 is mounted transversely 
between the side walls 62 of the frame. The slide table preferably 
includes a channel member 104 for adjustably receiving a pair of guide 
rails 106. The guide rails are spaced apart a distance which is 
approximately the same as the width of the sheet material 10. Mounted to 
each guide rail is a rigid shield 108. The shields are in opposed relation 
to each other and form a guideway for confining the feed path of the sheet 
material in such a way as to control wandering. The guide rails are 
mounted to the channel members in any suitable manner and can be adjusted 
for any desired width of the sheet material. The shields are preferably 
made from 18 gauge galvanized sheet metal or other suitable material and 
have side walls to provide rigidity. 
With reference to FIGS. 5, 5A and 5B, the press 20 includes two side walls 
120 and a pivot frame 122 pivotably mounted between the side walls. The 
pivot frame includes a front wall 124, two side braces 126 that are 
pivotably mounted to and extend rearwardly of the front wall, a rear brace 
128 extending transversely between the side braces and a pivot rod 129 
between and parallel to the front wall and the rear brace. The pivot rod 
extends transversely through the side braces and is rotatably mounted to 
the side walls. A strut 138 may also be added to connect the rear brace 
and the pivot rod to provide further support and rigidity. 
Mounted along each side wall is an air cylinder 130, each one pivotably 
connected to a respective end of the rear brace 128. Operation of the air 
cylinder raises the rear brace which causes the front plate to lower due 
to the see-saw action about the pivot rod. A counterweight 136 may be 
added to the rear brace if desired to restore the air cylinders to their 
lowered positions at the end of a pressing cycle. The control system 28 
controls the operation of a valve (not shown) connected to the air 
cylinders. The control system also operates the servo-drive motor, as will 
be discussed in detail below. 
With reference to FIGS. 6 and 7A-C, an upper die assembly 140 is mounted to 
the bottom of the front wall 124 of the pivot frame. A table 142 is 
located between the side walls of the press and receives a lower die 
assembly 144 in opposed relation to the upper die assembly. In order to 
insure proper alignment of the die assemblies during operation of the 
press, the lower die assembly is preferably provided with a bushing 148 at 
each end and the upper die assembly is provided with a post 149 at each 
end, which is slidably received in the respective bushing of the lower die 
assembly. 
The upper die assembly 140 includes an upper die mount 150, an upper 
retainer die 152 and an upper stripper pad 154 that extend transversely 
across the press. The retainer die is fastened to the die mount by 
fasteners 155. The stripper pad is secured to the retainer die by 
fasteners 156 that are provided in slots 157 to permit relative movement 
between the stripper pad and the retainer die, as will be described below. 
Notably, the stripper pad has two positions relative to the retainer die. 
A spring 158 between the two, biases the stripper pad in a spaced-apart 
relation from the retainer die. A downwardly facing surface 160 of the 
stripper pad is provided with a suitable dimple pattern (see FIGS. 8A and 
8B) for embossing the sheet material 10. 
Similarly, the lower die assembly 144 includes a lower die mount 162, a 
lower retainer die 164 and a lower stripper pad 166. The stripper pad of 
the lower die assembly also has two positions relative to its respective 
retainer die, and springs 165 between the two, bias the stripper pad in a 
spaced-apart relation to the retainer die. An upwardly facing surface 168 
of the lower stripper pad is provided with a dimple pattern that 
corresponds to the dimple pattern of the upper stripper pad. 
The dimple pattern is formed by a combination of pins 200 and grooves 202 
located in the upper and lower stripper pads. The pins are secured to 
their respective retainer dies and slide through grooves in the respective 
stripper pads when the press is operated. The pins may be disengaged, if 
desired, by sliding a tab 204 away from the die assembly 140. 
With reference also to FIGS. 8A and 8B, the sheet material is shown after 
it has been embossed. The preferred dimple pattern includes an alternating 
pattern of "hot dogs 204" and "hamburgers 206." In the embodiment shown, 
the "hamburgers" protrude out from the sheet material in both directions 
while the "hot dogs" only protrude in one direction. Such a dimple pattern 
is particularly beneficial in a heat exchanger core because it creates 
turbulence in the flow of air through the heat exchanger, which results in 
improved heat transfer. It will be appreciated that several other dimple 
patterns are suitable for providing the desired result. 
During operation of the press, the upper stripper pad 154 will contact the 
sheet material 10 and hold it against the lower stripper pad 166 for a 
brief moment (FIG. 7B) while the retainer dies 152, 164 close the gap 
caused by the spring bias (FIG. 7C). This sequence of events is beneficial 
in reducing the amount of sheet material that is pulled through the press 
during the embossing step because the stripper pads 154, 166 grip the 
sheet material and hold it in place just prior to the embossing. By 
reducing the likelihood that additional sheet material will be pulled 
through the press during operation, more accurate measurements may be made 
as to the width of the embossed pattern and the distance between 
consecutive embossed patterns. This is particularly important for 
coordinating the folding and cutting operations which occur subsequently, 
reducing errors relating to the height of the folds, locating the embossed 
pattern related to the folds, measuring the number of embossed patterns 
per fold and cutting of the sheet material into predetermined lengths. 
In order to control the press and coordinate its operation with the feed 
rollers of the feed control assembly, the press is provided with a pair of 
microswitches that monitor when the press is open or closed. One 
microswitch 210, shown schematically in FIGS. 7A-7C, is preferably mounted 
to the lower die assembly 144 in front of the front wall 124 and is 
actuated by the upper die assembly 140 when the press is closed (FIG. 7C). 
The other microswitch 212 also, shown schematically in FIGS. 7A-7C, is 
mounted to the side wall 120 of the press behind the front wall and is 
actuated by the upper die assembly 140 when the press is open (FIG. 7A). 
The signals from the microswitches are transmitted to the control system 
28 and are used to coordinate the operation of the press relative the 
operation of the feed control assembly and the pusher bar assembly, as 
will be described in more detail below. 
With reference to FIGS. 9 and 9A, the pusher bar assembly 22 includes a 
table 300, a pusher bar 302 and a stripper bar 306. Pusher bar assemblies 
are well known in connection with the manufacture of lamp shades and 
filter media, and are generally commercially available. One source for a 
pusher bar assembly is Geyer Manufacturing and Design, Inc. of Winamac, 
Ind. 
The pusher bar 302 of the present invention includes a pusher plate 308 
secured to a stabilizing bar 310 (see also FIGS. 10A and 10B), both of 
which extend transversely across the table. As will be described, during 
operation, the pusher plate is moved vertically between raised and lowered 
positions and is also moved toward and away from the stripper bar 306 
between a fold position, wherein the pusher plate is adjacent the stripper 
bar, and a feed position, wherein the pusher plate is spaced a 
predetermined distance from the stripper bar. 
To further rigidify the pusher plate 308, a frame 312 is mounted to the 
back of the pusher plate. The frame includes a support base 314 that 
extends transversely across the table. A pair of short columns 316 are 
mounted to the support base. Extending from the top of the columns toward 
the pusher plate are cantilevered arms 318. A distal end of each 
cantilevered arm preferably includes a cam wheel 320 against which the 
pusher plate rides when it is moved between its raised and lowered 
positions. 
The support base 314 of the frame 312 is mounted to a ball slide guidance 
system 338 which includes a slide 340 mounted to a rail 342 on each end of 
the table. See also FIGS. 10A and 10B. The rail is secured by brackets 341 
to the table. The slide includes bushings 343 mounted to a slide mount 
plate 344. The support base 314 of the frame 312 is mounted to the slide 
mount plate 344 by fasteners. The bushing contains one or more bearing 
cages containing bearings (not shown) to facilitate low friction movement 
along the rails. 
The pusher plate 308 is moved between its fold and feed positions by a 
servo-linear actuator 326 which provides precision control of the pusher 
plate. The servo-linear actuator is mounted to a bridge 328 that 
transverses the table, permitting the sheet material to be fed under the 
bridge to the pusher bar. The servo-linear actuator has a shaft 330, the 
distal end of which is secured to the pusher plate to effect movement of 
the pusher plate between the fold and feed positions. When the servo 
linear actuator is operated, the pusher plate moves along the rails 342 
toward and away from the stripper bar 306. 
Two vertically oriented air cylinders 350 are mounted to move the pusher 
plate 308 between its upper and lower positions. The control system 28 
controls the operation of a valve (not shown) connected to the air 
cylinders. Each vertically oriented air cylinder has a piston rod 352 
extending downwardly. The piston rod has a distal end that passes through 
the stabilizing bar 310 and bears on the slide mount plate 344 (see also 
FIG. 10A). It will be appreciated that when the piston rod is extended, 
the pusher plate is moved up to the raised position and when the piston 
rod is retracted, the pusher plate has moved down to its lowered position. 
In a preferred embodiment, a brass plate is preferably mounted across the 
table and fastened to the top of the slide mount plates 344 the bras plate 
will then move with the slide 340 along the surface of the table at low 
friction. The sheet of material 10 is pinched between the pusher plate 308 
and the brass plate 356 during the fold operation. 
The stripper bar 306 includes a stripper plate 360 and a stripper plate 
frame 362 that supports the stripper plate in opposed relation to the 
pusher plate. A pair of air cylinders 364 are mounted to each side of the 
stripper plate frame to permit raising and lowering of the stripper plate 
between its upper and lower positions. The control system 28 controls the 
operation of a valve (not shown) connected to the air cylinders. 
A microswitch 366 is also mounted along the pusher bar assembly and is 
actuated by the stripper bar when the stripper bar is in its raised 
position. Signals from the microswitch are transmitted to the control 
system 28 and are used to coordinate the operation of the pusher bar 
assembly as will be described below. 
The operation of the pusher bar assembly is shown in FIGS. 10A through 10F. 
In the feed position, the pusher plate 308 is spaced from the stripper 
plate 360 and is in its lowered position such that the pusher plate 308 
engages the sheet material (FIG. 10A). Notably, in order to prevent damage 
to the embossed pattern on the sheet material, the bottom surface of the 
stabilizing bar 310 is raised above the bottom edge of the pusher plate. 
Energizing the servo-linear actuator 326 moves the pusher bar to the fold 
position (FIG. 10B). If desired, a folding blade (not shown) may be 
inserted in the table midway between the pusher plate and the stripper 
plate to initiate the fold. See, e.g., U.S. Pat. No. 2,677,993. 
In the fold position, the pusher plate 308 is adjacent the stripper plate 
360 with a fold 370 of sheet material therebetween. Next, the stripper bar 
306 is raised to permit the fold to pass by (FIG. 10C). Preferably, the 
pusher plate 308 is moved slightly to push the fold past the stripper 
plate 360. The stripper bar is then lowered (FIG. 10D). Preferably, the 
stripper plate holds the sheet material in place while the pusher plate is 
raised (FIG. 10E). The pusher plate then is retracted to a location where 
the pusher plate is above its feed position (FIG. 10F) and lowered to the 
feed position (FIG. 10A) to repeat the process. 
To prevent damage to the embossed pattern in the sheet material 10, an 
inductive proximity sensor 380 is located on the pusher bar 302 to detect 
one of the dimples (see FIG. 10F). The sensor provides a signal to the 
control system 28 which then energizes the servo-linear actuator 326 to 
move the pusher bar a predetermined distance from the detected location to 
a location where the pusher plate 308 will fall between dimple patterns 
and avoid any damage to the dimples. 
For example, the press 20 can create a repeating two inch width dimple 
pattern in the sheet material with sufficient distance between each dimple 
pattern to permit placement of the pusher plate 308 between adjacent 
dimple patterns. Upon completion of a given fold operation, the control 
system can be programmed to energize the servo-linear actuator to move the 
pusher bar a predetermined distance from the stripper plate 360. Next, the 
sensor 380 is monitored and the pusher plate is slowly moved until the 
sensor detects a dimple. Once detected, the control system sends a signal 
to move the pusher plate a predetermined distance, which insures placement 
of the pusher plate at a location where it will not damage any dimples 
(usually between adjacent embossed patterns). 
The core cut-off assembly 24 is located past the pusher bar assembly 22 and 
includes a rotary blade saw 390 that is reciprocated transversely through 
a slot 392 across the table to separate the cores as they come out of the 
pusher bar assembly (See FIG. 1A). 
With reference again to FIGS. 1 and 1A, the control system 28 preferably 
includes a two-axis servo controller 400 that controls the servo-drive 
motor 68 for the feed rollers 18 and controls the servo-linear actuator 
326 for the pusher plate 308. Both the servo-drive motor 68 and the 
servo-linear actuator 326 provide positional feedback to the controller. 
The press microswitches 210, 212, the inductive proximity sensor 380 of 
the pusher bar assembly and the stripper bar microswitch 366, also provide 
signals to the controller. 
Based on the feedback signals, the controller 400 can be programmed to 
operate in a first loop to actuate the air cylinders 76 and the 
servo-drive motor 68 for the feed control rollers, and the air cylinders 
130 for the press 20. The controller can also be programmed to operate in 
a second loop to actuate the air cylinders 350 and the servo-linear 
actuator 326 for the pusher plate 308 and the air cylinders 364 for the 
stripper plate 360. 
The controllers, motors, actuators, sensors, microswitches and air 
cylinders mentioned above are well known in the art. For example, many are 
available from Parker Motion and Control of Rohnert Park, Calif. In 
addition, flow chart style programming software for programming the 
controller to operate in the types of loops described above is well known 
in the art. One preferred program is the Motion Builder software by Parker 
Motion and Control. Preferably, an operator interface (not shown) is also 
used to permit an operator to enter information into the two-axis servo 
controller 400. Such an operator interface is also available from Parker 
Motion and Control. 
Specifically, in the first loop, opening and closing of the feed rollers 18 
is coordinated with the press 20 to control wandering of the sheet 
material as the sheet material is fed through the press. For example, when 
the press is open, the microswitch 212 is activated and sends a signal to 
the controller 400. The controller then actuates the servo-drive 68 motor 
to feed a predetermined amount of sheet material through the press. Once 
completed, the servo-drive motor signals the controller that feeding is 
complete. At this time, the controller actuates the air cylinders 130 for 
the press, closing the press and also actuates the air cylinders 76 for 
the feed rollers 18, opening the rollers. Preferably, neither the press 20 
nor the feed rollers 18 engage the sheet material at this moment, 
permitting the sheet material to be guided to a centered position by the 
guide rails 106. (Alternatively, the press alone engages the sheet of 
material while the feed rollers do not, again permitting the sheet 
material to move to a centered position.) 
Once the press closes, the microswitch 210 is activated, sending a signal 
to the controller. The controller then turns off the air cylinders 130 for 
the press and the press opens due to the force of the counterweight 136 
(see FIG. 5A). The controller also actuates the air cylinders 76 for the 
feed rollers to close the rollers and the process loop repeats when 
microswitch 212 is activated. 
In the second loop, the positioning of the pusher plate 308 and the 
stripper plate 360, are coordinated to fold the sheet material. In 
addition, the movement of the pusher plate is controlled in such a manner 
to avoid damaging the embossed dimples on the sheet material. For example, 
the controller 400 can be programmed to start the loop when the pusher 
plate and the stripper plate are lowered onto the table in a nearly 
abutting position. The pusher plate air cylinders 350 are then actuated to 
raise the pusher plate, and the servo-linear actuator 326 is energized to 
move the pusher plate a predetermined distance from the pusher plate. The 
inductive proximity sensor 380 is then energized and the pusher plate is 
slowly moved to search for a dimple. Once a dimple is detected, the sensor 
sends a signal to the controller. A dimple is detected with this type of 
sensor when the sheet material is spaced a sufficient distance from the 
sensor, which will occur when the sensor passes over a recessed dimple, 
causing the sensor to turn off. 
Once the dimple is detected, the servo-linear actuator 326 is stopped. The 
controller is then programmed to actuate the servo-linear actuator again 
to quickly move the pusher plate a predetermined distance that will assure 
that the pusher plate will not land on a dimple when lowered. A feedback 
signal from the servo-linear actuator is provided to the controller once 
the pusher plate is moved the predetermined distance. The pusher plate air 
cylinders 350 are then actuated to lower the pusher plate onto the sheet 
material and the servo-linear actuator is operated to move the pusher 
plate against the stripper plate to fold the sheet material. The 
controller can be programmed to stop the pusher plate a predetermined 
distance from the stripper plate to prevent damage to the embossed dimples 
of the folded sheet of material. A feedback signal is provided to the 
controller, which then actuates the air cylinders 364 for the stripper 
plate, causing the stripper plate to open. The stripper plate microswitch 
366 then signals the controller that the stripper plate is open and the 
controller energizes the servo-linear actuator to push the fold past the 
stripper plate. The controller then receives another feedback signal from 
the servo-linear actuator that the movement is complete and the controller 
operates the air cylinder 364 to close the stripper plate, at which time 
the loop can repeat itself. 
Counters may be added to the loops to keep track of the number of embossed 
patterns completed per fold and the number of folds completed. This is 
particularly useful in reducing the amount of waste between the press and 
the pusher bar assembly. For example, the controller can be programmed to 
stop the press after the last core is formed, but permit the pusher bar 
assembly to continue until the core is folded. Although a substantial 
length of sheet material has been fed to the pusher bar assembly it is not 
embossed and may be reused. 
Similarly, the controller may be programmed to permit changes in fold 
height for consecutive cores or even change the fold height for the same 
core. In addition, cores can be made without embossed patterns or with 
certain portions of the cores unembossed, such as the end flaps, to assist 
in assembly of the heat exchanger. Yet another variation, is that the 
controller may be programmed to provide an unfolded, unembossed portion 
between cores to facilitate the cutting operation. 
In summary, the control system 28 controls and integrates the feed control 
assembly 15, the press 20 and the pusher bar assembly 22. The control 
system uses a motion builder program to control the servo amplifiers and 
all of the air cylinders. It also controls the timing of these components 
to automatically produce complete cores. The control system is programmed 
to produce automatically folded embossed cores, to produce cores with more 
than one fold height, to allow an unfolded section to be fed out between 
cores to allow for cut-off, to readily produce many different types of 
cores, to withhold the emboss pattern on the first and last fold of the 
core if desired and to produce non-embossed cores if desired. 
While a particular form of the invention has been illustrated and 
described, it will be apparent that various modifications can be made 
without departing from the spirit and scope of the invention. Accordingly, 
it is not intended that the invention be limited, except as by the 
appended claims.